There’s no doubt that Americans have the presidency on their minds this week. Yet a new exhibit turns to an important position that is often overlooked: the vice presidency.

“Presidents in Waiting,” which opened Tuesday at the National Portrait Gallery, focuses on the vice presidency and how it has evolved. The exhibit specifically looks at the 14 vice presidents who succeeded to the presidency by either winning an election, moving up after the death of an incumbent or, in one case, taking the job after a resignation.

The exhibit was organized by gallery historians Sidney Hart and James Barber. It was Barber’s idea to cover the vice presidency because it hadn’t been done before. “We thought Americans would want to think more about the vice presidency in relation to the presidency,” Hart said.

As Hart and Barber pointed out, about a third of the vice presidents have become president, a majority of them sworn in after their predecessor’s death.

As the exhibit shows, the vice presidency has changed drastically since it was first created. The only powers of the vice presidency were to preside over the Senate and break tie votes. A letter in the exhibit from John Adams to his wife, Abigail, says the vice presidency is “the most insignificant office that ever the invention of man contrived or his imagination conceived.” Yet Hart points out that Adams was still honored to have a position in such proximity to the power of the president. Ironically enough, he and George Washington were never close and discussed little, depriving Adams of extra responsibility and power that he could have been granted.

Barber discussed how the relationship between the president and vice president has changed since the mid-20th century. In the 2008 election, Americans looked to the compatibility between Sen. John McCain (R-Ariz.) and Alaska Gov. Sarah Palin (R), and now-President Barack Obama and now-Vice President Joseph Biden, but that was not the case in the past. “Many presidents [and their vice presidents] did not like each other at all,” Barber said. This was the case with Washington and Adams, as well as William Henry Harrison and John Tyler.

Before 1804, the vice presidency was not as much of a concern as it is now because the public could not vote specifically for the position. The exhibit explains that the vice presidency was awarded to the man who won the second most number of votes. The framers did not take into account the formation of political parties. The 1796 election resulted in Adams, a Federalist, and Democratic-Republican Thomas Jefferson as president and vice president, respectively. The pair had not only personal but also political tension. Often Jefferson would turn the Congress in opposition to Adams’ political agenda. The president and vice president were placed on one ticket in 1804, after the 12th Amendment was passed.

Looking at the more contemporary end of the exhibit, Hart explained how presidential mortality has been a concern for voters. “Americans realized that mortality could not be promised,” Hart said.

Particularly by Franklin D. Roosevelt’s election for his fourth term, word spread that he was not healthy and would die in office. One picture in the exhibit is of Harry Truman and Roosevelt at a White House luncheon after Truman was selected as a running mate. Afterward, Truman told the press that Roosevelt was absolutely fine and was still a strong leader. In reality, at the luncheon Truman watched a weakening Roosevelt spill cream into his saucer because of his uncontrollably shaking hand. The picture hides Roosevelt’s ill health very well, but rumors brought more attention to Truman as not only a vice presidential pick but also a possible president.

Despite Roosevelt’s ill health, he did not share that information with Truman. When the president passed away, Truman was only left with a briefing.

Hart explained Roosevelt’s thinking: “Because of their egos, most think they’re not going to die in office. They don’t think about that when picking the vice president.”

Dwight Eisenhower was another president who raised mortality as an issue. “His heart attack in ’55 was a real concern. Eisenhower wanted to prepare for succession so it would be more precise,” Hart said. This different approach in preparing a possible transition changed the role of the vice presidency by keeping Richard Nixon close and well-informed.

Over the years the vice presidential position continues to grow, but it still varies with each administration.

“It’s not a power position per se,” former President George H.W. Bush said in the exhibit’s video interview. “The only power you got is what the president says you should have.”

That does not mean that powerful men have demurred from accepting the position. Hart indicated many strong presidents first served as second in command: Theodore Roosevelt, Truman and Nixon, to name a few.

As the vice presidency grew, so did the country. “The exhibit shows the elevation and importance of not just the president but the vice president and how it’s connected to the U.S. becoming a world power,” Hart said.

Nevertheless, not all powerful vice presidents are guaranteed a position at the head of the ship.

“History does not say that will happen. You see, on this wall is Martin Van Buren, who won the election after serving under [Andrew] Jackson. The next vice president to be elected president is over here, George H.W. Bush. That’s a span of 152 years,” Hart said.

“In the foreseeable future, I see strong presidents and the power of the vice president derives from the president,” Hart said. Of course only the president can allot what power is given to the second in command. As Hart joked, historians are not experts at predicting the future. Only time will tell.

“Presidents in Waiting” will be open through Jan. 3, 2010.