BY LEIGH ANN CALDWELL, NBC News
(NBC News) - Their names aren't at the top of the ticket and they won't be the real stars on stage but Tim Kaine and Mike Pence face the same challenge in Tuesday night's vice presidential debate according to strategists from both parties -- to reinforce negative opinions of their opponents and to ease voter concerns about the top of their own tickets.
GOP nominee Donald Trump and Democratic standard-bearer Hillary Clinton are the most unpopular presidential candidates in modern history, opinions among voters that have only hardened after more than a year spent on the campaign trail.
Meanwhile, the two running mates are among the least known vice presidential candidates in recent elections. Remember Sarah Palin, Dick Cheney and even Joe Biden? Of course. But many voters in 2016 have never heard of Clinton's and Trump's number two. In the latest NBC/WSJ poll, 55 percent of respondents either didn't know enough about Kaine to form an opinion about him or were completely neutral. And 49 percent said the same thing about Pence.
But tonight's debate isn't about them.
For Pence, the GOP governor of Indiana, the task is especially large. Trump has come off one of the worst weeks in presidential campaigns and Pence will have to defend -- or explain -- much of it. Bad reviews from the first presidential debate, attacks on a former Miss Universe and a perplexing campaign appearance over the weekend have the GOP nominee down in the most recent round of polling.
And Pence, who has released his own tax returns, will likely be asked to explain why, according to tax analysis of documents received by the New York Times, Trump may have used nearly $1 billion in losses to potentially avoid paying federal taxes for up to a decade.
"He does need to look and sound respectable and rational while defending the irrationality of Donald Trump," said Ryan Williams, Republican strategist at FP1 Strategies who worked for Mitt Romney's 2012 presidential campaign. "He has a very fine line to walk."
Kaine also must make up for what his nominee lacks. Unlike many perceptions of Clinton, Kaine is seen as earnest, trustworthy, and likeable. After his speech at the Democratic National Convention, political reporters and strategists joked on social media that he is the epitome of "dad jokes" - corny but loveable.
"He emanates a decency that is often lacking in modern politics," said Lis Smith, former campaign aide for numerous Democratic presidential candidates.
Only 31 percent of Americans perceive Clinton as more "honest and straightforward" than Trump, according to the September NBC/Wall Street Journal, reinforcing the ongoing perception that has dogged her campaign largely because of continued questions about her private email server and dealings at the Clinton foundation. Meanwhile, only 23 percent of respondents in the same poll said Trump has the "right temperament" to be president.
And that's a big part of why Pence and Kaine were chosen to balance out the top of the of the ticket. With Trump's bombast and unpredictability, Pence is the exact opposite. A former member of Congress and current governor of Indiana, Trump chose him among people being considered because he is calm, collected, conservative and, well, conventional.
"Pence needs to change the narrative from this discussion of Donald Trump's personal foibles and get it back on the concerns of the average voter," said Republican strategist John Feehery. "He's gotta use his reputation to say that Trump is a good guy... and he has to give examples of that."
Because Pence and Kaine are so different from Trump and Clinton, the vice presidential debate is expected to be much different from last week's presidential face-off that left Trump mostly on the defensive. Trump was unable to keep the focus on Clinton's emails, her family's foundation or her tenure as Secretary of State. Instead the 90-minute debate was mostly memorable for discussions about Trump -- his business record, his taxes, his treatment of women and his birther crusade.
Rodell Mollineau, a Democratic strategist at Rokk Solutions, predicts Pence will be a much better debater than Trump.
"Pence is going to throw a lot of attacks on Kaine about Clinton," Mollineau said. "Kaine needs to forcefully defend our nominee."
While both candidates' primary goal is to reassure skeptical voters that their ticket can be trusted and that they compensate for the presidential candidates' perceived weaknesses, a secondary goal will be to drive home policy differences. Because both Pence and Kaine, with long histories of governing, are well steeped in policy, this could be the most substantive debate of any of the three presidential debates.
Viewers could very well hear more details about policy from the vice presidential candidates than what voters have heard from Trump and Clinton on a wide range of issues, from trade to foreign policy, job creation, abortion and LGBTQ rights.
And strategists on both sides of the ideological aisle predict that Kaine and Pence will try to highlight the differences they've each had with their own running mates. Clinton and Kaine have diverged on issues of trade, the death penalty and abortion while Trump and Pence have differed also on trade and LGBTQ rights.
Still, Maria Cardona, Democratic strategist at Dewey Square Group, said that in the wake of Trump's rough week, Kaine has the upper hand.
"Mike Pence can certainly try to have some semblance of coherence and decency to the conversation that has been absent, but what Tim Kaine will continue to remind peoples is that Mike Pence is not running, Donald Trump is running for president," Cardona said.