Aug. 15, 2012 -- With Rep. Paul Ryan joining the Republican ticket as the candidate for vice president, both parties have put into place the men who will lead the country over the next four years. Ryan is vying to replace current Vice President Joe Biden.
Although a vice president can arguably have an impact on polling numbers when they're initially introduced, once they're on the job, they have seemingly fewer responsibilities than they did on the campaign trail.
The vice president's duty is to be ready to serve as president should the need arise, and to preside over the Senate, casting a vote in the case of a tie.
That's about it.
Despite the limits of the position on paper, some vice presidents have used the job to great effect.
John Adams, the first-ever vice president of the United States, set the standard of using the post as a stepping stone to the big office. Had Adams gotten his way, he would have been the country's first president instead of George Washington.
Adams also established the tradition of the vice presidency being essentially a do-nothing gig. Washington didn't include Adams in the decisions of the administration, leaving Adams to his work in the Senate, where the vice president's presence is uninvolved unless there's a tie.
For a man of Adams' ambition, he was ill-suited to the office. In a letter to the wife, he even called the vice presidency "the most insignificant office that ever the invention of man contrived or his imagination conceived."
In Abraham Lincoln, the United States got a leader widely considered to be the greatest president in U.S. history. Lincoln's choice of vice president for his reelection bid, Andrew Johnson, would prove to be one of the worst.
As a Democrat and a Southerner who supported the Union, Johnson appeared to be Lincoln's perfect candidate to convey the message of unity.
Johnson held the office for a little more than a month before Lincoln was assassinated and he became president. Johnson's bungled efforts at post-Civil War Reconstruction and later impeachment cemented his place among the worst leaders to hold the office of the presidency.
Gov. Theodore Roosevelt proved to be too much of a handful for business leaders in the state of New York. According to his Senate biography, Roosevelt "supported legislation authorizing the state supreme court to inspect the books of corporations, endorsed anti-monopoly legislation, pushed for better civil service laws, supported an eight-hour-day law for public employees, and advocated a minimum wage for New York City's school teachers."
Given that Roosevelt proved popular with the people, unseating him couldn't be done at the voting booth. Instead, Roosevelt, supported by both friends and critics, was encouraged to pursue the office of the vice presidency.
Roosevelt initially had his doubts, since as vice president, he "could not do anything," unlike his tenure as governor. He eventually accepted the spot on William McKinley's ticket, pleasing both his supporters and detractors.
Six months into his second term, McKinley was assassinated. Roosevelt took over as president, where he continued some of the same policy trajectories he began as governor.
Harry Truman never wanted the job of vice president. As fate would have it, he wouldn't hold onto the job for very long anyway.
Truman had to be pressured by then-President Franklin D. Roosevelt to accept the number two spot on his ticket for the 1944 presidential election, replacing then-Vice President Henry Wallace, who was deemed too liberal for the post in war time given Roosevelt's deteriorating health.
Truman's three-month tenure as vice president didn't produce many achievements. On April 12, 1945, Roosevelt died, and Truman was sworn in as president. Shortly after taking office, Truman heard about a secret project to test what would be the most destructive weapon in human history: the atomic bomb.
As president, Truman would give the order to drop the atomic bomb on Hiroshima and Nagasaki, forcing Japan to surrender and bringing an end to World War II in the Pacific Theater.
Before Richard Nixon even assumed the vice presidency, he left his mark on the campaign trail.
In 1952, amidst allegations of possible conflicts of interest due to a fund he had created for political donors to reimburse him for expenses, Nixon came under fire. Rather than resign, Nixon fought back in a famous televised address, now known as the "Checkers speech," delivered to some 60 million viewers.
Nixon portrayed himself as firmly middle class, unlike his wealthy Democratic opponents. He also noted that all donations went strictly to his political work, and he did not in any way profit from it. The one exception, however, was a gift from a man from Texas: "It was a little cocker spaniel dog in a crate that he'd sent all the way from Texas. Black and white spotted. And our little girl -- Tricia, the 6-year-old -- named it Checkers."
Reactions to the speech were mixed, with Nixon's defenders calling it a tour de force and his detractors claiming it was an exercise in emotional manipulation.
In order to gain the support of southern Democrats for his election bid and mollify critics who though then-Sen. John F. Kennedy was too inexperienced for the presidency, the Massachusetts politician needed Texas Senator Lyndon B. Johnson on his ticket.
As vice president, Johnson had to adjust to the lack of influence he enjoyed as a Senator. Still, Johnson is credited with being an advocate for civil rights and the space program while he held the office.
On Nov. 22, 1963, Kennedy was assassinated. Johnson was sworn in during a hasty ceremony aboard Air Force One.
As president, Johnson furthered his legacy as a civil rights supporter, pushing Congress to pass the Civil Rights Act of 1964, a move Johnson predicted would cost Democrats the south for a generation.
Johnson's Great Society also pushed through sweeping changes to the government's role in Americans' lives, which included programs like Medicare and Medicaid and funding for education and combating poverty.
No matter what your politics, there's no arguing that Dick Cheney represented the office unlike any of his predecessors.
Dubbed "the most influential and powerful man ever to hold the office of the vice presidency" by the Washington Post, Cheney always took a front seat in crafting administration policy on every issue from national security to foreign affairs to the environment and more.
As Barton Gellman and Jo Becker detail in a Pulitzer-winning series about the former vice president, Cheney's years in Washington in both Congress and previous administrations had made him a master of bureaucracy.
His view on the limits and privileges of executive power took shape early in his career, when he served under the Nixon administration, and would transform the office of the presidency during the eight years he worked under President George W. Bush.
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