Eligibility
Unlike the president, the Constitution does not specify an oath of office for the vice president. Several variants of the oath have been used since 1789; the current form, which is also recited by Senators, Representatives and other government officers, has been used since 1884:
The phrase "so help me God" is optional, as it is in any oath of office in the United States of America. The original oath taken by the vice president was signed into law by George Washington on June 1, 1789. It did not include the phrase "so help me God." The use of a religious codicil was introduced by Congress when it devised the Ironclad Test Oath, which was signed into law on July 2, 1862.

Oath
Under the original terms of the Constitution, the members of the U.S. Electoral College voted only for office of president rather than for both president and vice president. Each elector was allowed to vote for two people for president. The person receiving the greatest number of votes (provided that such a number was a majority of electors) would be president, while the individual who was in second place became vice president. If no one received a majority of votes, then the U.S. House of Representatives would choose among the five highest vote-getters, with each state getting one vote. In such a case, the person who received the highest number of votes but was not chosen president would become vice president. If there was ever a tie for second, then the U.S. Senate would choose the vice president.
The original plan, however, did not foresee the development of political parties. In the election of 1796, for instance, Federalist John Adams came in first, and Democratic-Republican Thomas Jefferson came second. Thus, the president and vice president were from different parties. An even greater problem occurred in the election of 1800, when Democratic-Republicans Jefferson and Aaron Burr tied the vote. While it was intended that Jefferson was the presidential contender and Burr was the vice presidential one, the electors did not and could not differentiate between the two under the system of the time (Article Two, Clause 3). The plan had been for one elector to vote for Jefferson but not Burr, thus giving Burr one fewer vote. This plan broke down for reasons that are disputed. After 35 unsuccessful votes in the U.S. House of Representatives, Thomas Jefferson finally won on the 36th ballot and Burr became vice president.
The tumultuous affair led to the adoption of the Twelfth Amendment in 1804, which directed the electors to use separate ballots to vote for the president and vice president. While this solved the problem at hand, it ultimately had the effect of lowering the prestige of the vice presidency, as the vice president was no longer the second choice for president.
The Constitution also prohibits electors from voting for both a presidential and vice presidential candidate from the same state as themselves. In theory, this might deny a vice presidential candidate with the most electoral votes the absolute majority required to secure election, even if the presidential candidate is elected, and place the vice presidential election in the hands of the Senate. In practice, this requirement is easily circumvented by having the candidate for vice president change the state of residency as was done by Dick Cheney, who changed his legal residency from Texas to Wyoming, his original home state, in order to run for election as vice president alongside George W. Bush, who was then the governor of Texas.
Formally, the vice presidential candidate is nominated by the party convention. However, it has long been the custom that the vice presidential candidate has been effectively named by the presidential nominee. Often, the presidential nominee will name a vice presidential candidate who will bring geographic or ideological balance to the ticket or appeal to a particular constituency. The vice presidential candidate might also be chosen on the basis of adding foreign or domestic policy experience to the ticket, or on the basis of a particular vice presidential candidate's name recognition. The last presidential candidate to not name his vice presidential choice was Democrat Adlai Stevenson in 1956. Stevenson left the choice up to the convention, which chose Tennessee Senator Estes Kefauver over Massachusetts Senator (and later president) John F. Kennedy.
Election

Role of the Vice President
The formal powers and role of the vice president are limited by the Constitution to becoming President in the event of the death or resignation of the President and acting as the presiding officer of the U.S. Senate. As President of the Senate, the Vice President has two primary duties: to cast a vote in the event of a Senate deadlock and to preside over and certify the official vote count of the U.S. Electoral College. For example, in the first half of 2001, the Senators were divided 50-50 between Republicans and Democrats and Dick Cheney's tie-breaking vote gave the Republicans the Senate majority. (See 107th United States Congress.)
The informal roles and functions of the Vice President depend on the specific relationship between the President and the Vice President, but often include drafter and spokesperson for the administration's policy, as an adviser to the president, as Chairman of the Board of the National Aeronautics and Space Administration (NASA), as a Member of the board of the Smithsonian Institution, and as a symbol of American concern or support. Their influence in this role depends almost entirely on the characteristics of the particular administration. Cheney, for instance, is widely regarded as one of George W. Bush's closest confidantes. Al Gore was an important advisor to President Bill Clinton on matters of foreign policy and the environment. Often, Vice Presidents will take harder-line stands on issues to ensure the support of the party's base while deflecting partisan criticism away from the President. As under the American system the president is both head of state and head of government, the ceremonial duties of the former position are often delegated to the Vice President. He or she may meet with other heads of state or attend state funerals in other countries, at times when the administration wishes to demonstrate concern or support but cannot send the President himself.
In recent years, the vice presidency has frequently been used to launch bids for the presidency. Of the 13 presidential elections from 1956 to 2004, nine featured the incumbent president; the other four (1960, 1968, 1988, 2000) all featured the incumbent vice president. Former vice presidents also ran, in 1984 (Walter Mondale), and in 1968 (Richard Nixon, against the incumbent Vice President Hubert Humphrey).
Since 1974, the official residence of the vice president and his family has been Number One Observatory Circle, on the grounds of the United States Naval Observatory in Washington, DC.

Duties

Main article: President of the Senate President of the Senate
For much of its existence, the office of Vice President was seen as little more than a minor position. John Adams, the first vice president, described it as "the most insignificant office that ever the invention of man contrived or his imagination conceived." Even 150 years later, 32nd Vice President John Nance Garner famously described the office as "not worth a pitcher of warm piss" (at the time reported with the bowdlerization "spit"). Thomas R. Marshall, the 28th Vice President, lamented: "Once there were two brothers. One went away to sea; the other was elected vice president. And nothing was heard of either of them again." When the Whig Party was looking for a vice president on Zachary Taylor's ticket, they approached Daniel Webster, who said of the offer "I do not intend to be buried until I am dead." The natural stepping stone to the Presidency was long considered to be the office of Secretary of State. It has only been fairly recently that this notion has reversed; indeed, the notion was still very much alive when Harry Truman became the vice president for Franklin Roosevelt.
For many years, the vice president was given few responsibilities. After John Adams attended a meeting of the president's Cabinet in 1791, no Vice President did so again until Thomas Marshall stood in for President Woodrow Wilson while he traveled to Europe in 1918 and 1919. Marshall's successor, Calvin Coolidge, was invited to meetings by President Warren G. Harding. The next Vice President, Charles G. Dawes, was not invited after declaring that "the precedent might prove injurious to the country." Vice President Charles Curtis was also precluded from attending by President Herbert Hoover.
In 1933, Roosevelt raised the stature of the office by renewing the practice of inviting the vice president to cabinet meetings, which has been maintained by every president since. Roosevelt's first vice president, John Nance Garner, broke with him at the start of the second term on the Court-packing issue and became Roosevelt's leading political enemy. Garner's successor, Henry Wallace, was given major responsibilities during the war, but he moved further to the left than the Democratic Party and the rest of the Roosevelt administration and was relieved of actual power. Roosevelt kept his last vice president, Harry Truman, uninformed on all war and postwar issues, such as the atomic bomb, leading Truman to wryly remark that the job of the vice president is to "go to weddings and funerals." The need to keep vice presidents informed on national security issues became clear, and Congress made the vice president one of four statutory members of the National Security Council in 1949.
Richard Nixon reinvented the office of vice president. He had the attention of the media and the Republican party, and Eisenhower ordered him to preside at Cabinet meetings in his absence. Nixon was also the first vice president to temporarily assume control of the executive branch; he did so after Eisenhower suffered a heart attack on September 24, 1955; ileitis in June 1956; and a stroke in November 1957.
President Jimmy Carter was the first president to formally give Walter Mondale, his vice president, an office in the West Wing of the White House.
Despite the mostly minor role, some vice presidents—in addition to the aforementioned Nixon and Mondale—have been regarded as powerful politicians while in office (i.e., Martin Van Buren, George H.W. Bush, Al Gore, and Dick Cheney).

Growth of the office
The U.S. Constitution provides that should the president die or become disabled while in office, the "powers and duties" of the office are transferred to the vice president. Initially, it was unclear whether the vice president actually became the new president or merely acting president. This was first tested in 1841 with the death of President William Henry Harrison. Harrison's Vice President, John Tyler, asserted that he had succeeded to the full presidential office, powers, and title, and declined to acknowledge documents referring to him as "Acting President." Despite some strong calls against it, Tyler took the oath of office, becoming the tenth president. Tyler's claim was not challenged legally, and so the precedent of full succession was established. This was made explicit by Section 1 of the 25th Amendment to the U.S. Constitution, ratified in 1967.
One issue that could not be addressed without the adoption of a constitutional amendment was the status of the vice presidency in the event that the vice president died in office, resigned, or succeeded to the presidency. The original Constitution had no provision for selecting a replacement, so the office of vice president remained vacant until the beginning of the next presidential and vice presidential terms. This issue had arisen most recently with the assassination of President Kennedy on November 22, 1963, and was rectified by section 2 of the 25th Amendment.
The other remaining issue was the question of who has the power to declare that an incapacitated president is unable to discharge his duties. This question had arisen most recently with the illnesses of President Dwight D. Eisenhower. Sections 3 and 4 of the 25th Amendment provided procedures for the transfer of power to the vice president in case of presidential disability.
Section 2 of the 25th Amendment provides that "Whenever there is a vacancy in the office of the Vice President, the President shall nominate a Vice President who shall take office upon confirmation by a majority vote of both Houses of Congress." Gerald Ford was the first Vice President selected by this method, after the resignation of Vice President Spiro Agnew in 1973; after succeeding to the Presidency, Ford nominated Nelson Rockefeller as vice president.
Sections 3 and 4 of the amendment provide means for the vice president to become Acting President upon the temporary disability of the president. Section 3 deals with self declared incapacity of the president, and section 4 deals with incapacity declared by the joint action of the Vice President and of a majority of the Cabinet. While section 4 has never been invoked, section 3 has been invoked three times: on July 13, 1985 when Ronald Reagan underwent surgery to remove cancerous polyps from his colon, and twice more on June 29, 2002 and July 21, 2007 when George W. Bush underwent colonoscopy procedures requiring sedation. Prior to this amendment, Vice President Richard Nixon informally replaced President Dwight Eisenhower for a period of weeks on each of three occasions when Eisenhower was ill.

Succession and the 25th Amendment
Prior to ratification of the 25th Amendment in 1967, no provision existed for filling a vacancy in the office of vice president. As a result, the vice presidency was left vacant 16 times (sometimes for nearly four years) until the next ensuing election and inauguration -- 8 times due to the death of the sitting president, resulting in the vice president becoming president; 7 times due to the death of the sitting vice president, and once due to the resignation of VP John Calhoun to become a senator. Since the adoption of the 25th Amendment, the office has been vacant twice while awaiting confirmation of the new vice president by both houses of Congress.

Vice Presidents of the United States of America

List of Vice Presidents
Acted as President under provisions of 25th Amendment

Notes
Longevity
Age while in office
Two served under two different Presidents
Seven died in office
Two resigned
Three were the apparent target of an assassination attempt (all three unsuccessful)
Two shot a man while serving as Vice President
Two were never elected to the office
Nine succeeded to the Presidency
Four sitting Vice Presidents were elected President
One non-sitting former Vice President was elected President Richard Nixon was elected President in 1968. He had been Vice President to Eisenhower from 1953 to 1961.
Nixon is also the only person to be elected as Vice President for two terms and President for two terms (although he did not complete his second term as President). Nixon being unable to serve a second full term means that as yet no one has ever served two full terms both as Vice President and then as President.
Two have been Acting President
They officially acted as President due to presidential incapacity under the 25th Amendment.
Living former Vice Presidents
Of these, Bush was later elected President. Mondale and Gore were nominated by their parties, and ran for President unsuccessfully (Gore won the popular vote but lost the electoral vote against George W. Bush in the 2000 presidential election), while Quayle was unable to get the necessary support in order to do so.
Three were named Johnson
Three were born on August 27
Seven served two full terms

John Nance Garner was two weeks shy of his 99th birthday when he died.
Levi Morton died on his 96th birthday.
Gerald Ford died at the age of 93.
John Adams died at the age of 90.
John C. Breckinridge, the youngest ever to serve, was 36 when he became vice president in 1857.
Alben W. Barkley, the oldest ever to serve, was 75 when he left the vice presidency in 1953.
George Clinton under Thomas Jefferson and James Madison
John C. Calhoun under John Quincy Adams and Andrew Jackson
George Clinton in 1812
Elbridge Gerry in 1814
William Rufus de Vane King in 1853
Henry Wilson in 1875
Thomas Hendricks in 1885
Garret Hobart in 1899
James Sherman in 1912
John C. Calhoun resigned on December 28, 1832 to take a seat in the Senate, having been chosen to fill a vacancy.
Spiro Agnew resigned on October 10, 1973 upon pleading no contest to charges of accepting bribes while governor of Maryland.
Andrew Johnson was a target of the same conspiracy which murdered President Abraham Lincoln and attempted to murder Secretary of State William H. Seward
Thomas R. Marshall was a target of letter bomb in 1915
Dick Cheney was in the vicinity of a bomb allegedly meant for him.
Aaron Burr shot and killed Alexander Hamilton in a duel on July 11, 1804; see Burr-Hamilton duel.
Dick Cheney accidentally shot Harry Whittington in the face while hunting quail on February 11, 2006; see Dick Cheney hunting incident.
Gerald Ford was nominated to office upon the resignation of Spiro Agnew in 1973.
Nelson Rockefeller was nominated to office upon the succession of Gerald Ford to the Presidency in 1974.
John Tyler became President when William Harrison died. Chose not to seek full term.
Millard Fillmore became President when Zachary Taylor died. Sought the Whig nomination in 1852, but lost to Winfield Scott. Four years later, ran and lost as the candidate of the American and Whig Parties.
Andrew Johnson became President when Abraham Lincoln was assassinated. Sought the Democratic nomination in 1868, but was unsuccessful.
Chester A. Arthur became President when James Garfield was assassinated. Sought a full term, but was not re-nominated.
Theodore Roosevelt became President when William McKinley was assassinated; then was elected to full term. Didn't seek re-election. Four years after leaving office, ran again and lost.
Calvin Coolidge became President when Warren Harding died; then was elected to full term. Did not seek re-election.
Harry Truman became President when Franklin Roosevelt died; then was elected to full term. Did not seek re-election.
Lyndon Johnson became President when John Kennedy was assassinated; then was elected to full term. Did not seek re-election.
Gerald Ford became President when Richard Nixon resigned; then lost election to full term.
John Adams (1789-1797) was elected President in 1796.
Thomas Jefferson (1797-1801) was elected President in 1800.
Martin Van Buren (1833-1837) was elected President in 1836.
George H. W. Bush (1981-1989) was elected President in 1988.
George H. W. Bush acted as President for Ronald Reagan on July 13, 1985.
Dick Cheney has acted twice as President for George W. Bush, on June 29, 2002 and July 21, 2007.
Walter Mondale
George H. W. Bush
Dan Quayle
Al Gore
Richard Mentor Johnson
Andrew Johnson
Lyndon Johnson
Hannibal Hamlin (1809)
Charles Dawes (1865)
Lyndon Johnson (1908)
John Adams
Daniel Tompkins
Thomas R. Marshall
John Garner
Richard Nixon
George H.W. Bush
Al Gore Orthographic style

Vice Presidential Service Badge
Second Lady of the United States- "Second Lady" is the unofficial title given to the Vice President's wife.