The vice presidential debate Tuesday could carry with it the same impact that Republican Mike Pence and Democrat Tim Kaine have each brought to their respective tickets: inconsequential.

Political experts have said for years that voters make their choice based solely on presidential candidates and not the No. 2 picks. But this year, they are also wondering if the men that Republican Donald Trump and Democrat Hillary Clinton have selected to run alongside them are as unimportant as any pair in modern political times.

In 2012, Mitt Romney's pick, Paul Ryan, served as an important figure in the domestic budget debate during negotiations to avoid a government shutdown. In 2008, Sarah Palin initially brought good energy to the ticket — and then months of bad headlines. In 2004, John Edwards used his perch to politically prosecute Vice President Dick Cheney on his role in the war in Iraq.


In some years, the vice presidential picks had an impact because they were bad (see Quayle, Dan: 1988). Other years the vice presidential candidates were seen has terrific (see Mondale, Walter: 1976). Some picks were interesting, like in 1984, which had the first female on the ticket (Geraldine Ferraro), and in 2000, which had the first Jewish nominee (Joe Lieberman).

At least those picks had some impact on the race, however limited.

"I think this campaign is, to an unusual degree, about the presidential candidates and the vice presidential candidates are probably getting less focus than is normally the case," said Joel Goldstein, a professor at the Saint Louis University School of Law and a specialist on vice presidents.

It has been two months since America met Pence, Indiana's governor, and Kaine, a US Senator from Virginia. At the time both picks appeared to be politically logical.

Pence, a onetime leadership lieutenant in the House, is an establishment Republican and social conservative who could balance Trump's flippancy on gay marriage and abortion. Trump's campaign viewed Pence as someone who could vouch for him with the party's most apprehensive and conservative Republicans.


Kaine, meanwhile, was perceived as the safe pick. Clinton didn't pick a candidate to excite the base. She picked a candidate who backed her 2008 rival, President Obama, and who had the experience to be president. Democrats also hoped Kaine could put Virginia, a swing state, squarely in their party's column.

Looking back, however, neither have accomplished these missions.

Days before Pence was picked for the ticket in July, 24 percent of Republicans had an unfavorable view of Trump. In the most recent Washington Post-ABC News poll, taken last week, 23 percent.

Similarly, Democrats have failed to put Virginia in the bank. Prior to Kaine's addition to the ticket, two July polls showed Clinton leading Trump in Virginia in the high single digits. After he was picked, Clinton bumped up in state surveys by another few points, but the most recent surveys show her in the high single digits again, leading Trump by 6 or 7 percentage points.

Nathan Gonzales, a nonpartisan political analyst and publisher of the Rothenberg & Gonzales Political Report, said that Pence doesn't change which states Trump can win — but he does help Republican candidates for governor or Congress. He said they can appear on the same big stage with the national ticket without having to stand next to Trump.


As for the Democrats, Gonzales said, "Clinton would have been in strong position in Virginia with or without Tim Kaine on the ticket."

Of course it might be unfair to expect either Kaine or Pence to break through in this particular year. Both Clinton and Trump are among the most well-known presidential nominees in history. Voter perceptions of them — which are mostly negative — have been baked into the nation's mind for a long time.

These running mates face additional challenges in getting attention.

Kaine — through no fault of his own — is about the sixth most popular Democrat to headline a rally for Clinton, behind the candidate herself, Bill Clinton, Barack Obama, Michelle Obama, and Vice President Joe Biden.

On the Republican side, Trump has essentially taken away a traditional running mate role from Pence: The attack dog. It's clear that Trump prefers to do this himself.

"Since Trump is the professional attacker, it has relegated Pence to playing more of a behind-the-scenes role with conservatives and the so-called establishment types that doesn't get a lot of attention," said Republican consultant Ryan Williams, who worked on Romney's presidential campaign.

While the first presidential debate between Trump and Clinton was the most watched in American history, Tuesday's sole vice presidential debate could be the most ignored.

However, Goldstein, who has written two books on the vice presidency, said that history has proven that sometimes the debate itself can launch political careers.


But it's all relative. The next week's debate will put more attention on Kaine and Pence that they have received all campaign.

"That may elevate one or both of them," Goldstein said.

James Pindell can be reached at james.pindell@globe.com. Follow him on Twitter @jamespindell or subscribe to his daily e-mail update on the 2016 campaign at www.bostonglobe.com/groundgame