Running mates don't matter much - except Trump's

John Nance Garner, a blunt Texan who served as the 32nd vice president of the United States, did not mince words about what he thought of the office. The vice presidency, he famously said, is "not worth a bucket of warm piss," adding that taking on the role was the "worst damn fool mistake I ever made."

Until Jimmy Carter picked Walter Mondale 40 years ago as his running mate, vice presidents did play a very limited role. They had two key functions, one of which was their clichéd status of being "a heartbeat away from the presidency." Their second constitutional role was to serve as president of the Senate. As a result of their limited duties and the job's low esteem, vice presidents were often relegated to playing second fiddle next to an overbearing president. Or put more succinctly by former President and Vice President Harry Truman, vice presidents are "about as useful as a cow's fifth teat."

Elevated role

Jimmy Carter changed much of that perception. Not only did he give Mondale a leading role in his presidential campaign, even more importantly, Carter publicly elevated Vice President Mondale by giving him his own West Wing office and making him a key presidential advisor.

Since then vice presidents don't just fly to state funerals and wait around for the president to die, but serve as crucial confidants of the president, said Matt Dickinson, an expert on the US presidency at Middlebury College. Based on their individual background and expertise, they can help mitigate potential deficiencies of the candidate.

To do just that, George W. Bush, a president without prior Washington or national security experience relied - for better or worse - on Dick Cheney's expertise and advice on those matters. Likewise, Barack Obama, a president without much Congressional experience, selected longtime Senator Joe Biden to help him deal with Congress.

"The vice president has really moved into the executive branch," noted Joel Goldstein, a scholar of the vice presidency at Saint Louis University.

Little electoral impact

While the vice president has become a significantly more important political player in the last four decades, the same cannot be said about the impact of vice presidential candidates on the election outcome.

"Vice presidents generally do not matter much over all," said Dickinson. "The best evidence we have is that the running mate can influence the vote at the margins."

For that to happen, the vice presidential pick usually needs to hail from a so-called swing state, i.e. a state that is potentially up for grabs in the election. The running mate's home state advantage and popularity, goes the argument, could make the difference in a close race.

"That's the best scenario for picking a vice president strategically," said Dickinson. "Pick one from a swing state that's in play and you might get a marginal boost. Otherwise we don't see much electoral impact."

In other words, vice presidential candidates can provide a limited regional bonus, but usually don't have a measurable positive impact on the national race.

Wrong pick

But there can also be a downside if you choose the wrong person to run on your ticket.

"If one of the presidential candidates' picks somebody who is not ready for prime time it can make a difference at the margins," said Goldstein.

As an example for a running mate with a negative impact on the ticket, Dickinson mentions Republican candidate John McCain's controversial vice presidential pick Sarah Palin."There is some evidence that in 2008 Sarah Palin may have depressed support for McCain slightly."

Applied to the current race, the strategic logic of choosing a vice president would have Hillary Clinton not pick liberal favorite Senator Elizabeth Warren as her running mate. While Warren would excite Bernie Sanders' supporters, her home state of Massachusetts is solid Democratic turf and thus electorally uninteresting.

Better picks would be Senator Tim Kaine from Virginia or Senator Sherrod Brown from Ohio, both swing states. Brown, a liberal, would have the additional benefit that he - like Warren - could shore up Clinton's perceived weakness, namely her problems with progressive voters.

Trump needs a solid running mate

While selecting the right vice presidential candidate is important, but not crucial for an experienced political player like Clinton, it is critical for Trump.

"In recent history I can't think of a candidate who is more in need of choosing a vice president who can compensate for his apparent weaknesses, which in Trump's case is an absolute lack of any governing experience whatsoever at the national level," said Dickinson. "You cannot overstate the significance of who he picks, not just electorally, but in a governing sense as well."

The problem is that the people Trump needs - GOP heavyweights from swing states with Washington experience - are not exactly lining up to become his vice presidential candidate. John Kasich, a former US congressman and current governor of Ohio, would arguably be Trump's best pick.

But Kasich, a former presidential candidate himself, has been highly critical of Trump and refused to endorse him. Like many key Republican figures, he does not even plan to attend his party's nominating convention.

That leaves people like former House Speaker Newt Gingrich or Senators Bob Corker and Jeff Sessions, who may be open to run with Trump. While they all possess Washington experience, they all hail from safe Republican states in the South - not exactly the region where Trump needs to get a boost.

Based on his background, temperament and Twitter habits, Newt Gingrich, a former history professor and twice divorced Roman Catholic convert might perhaps be the best match for Trump.