When Republican Mike Pence goes on stage on Tuesday against Democrat Tim Kaine in their vice-presidential debate, is he likely to defend his presidential nominee Donald Trump as a "genius" for ducking income tax, as have so many campaign surrogates?
Probably, if that's the party line. But something inside him may cringe. Pence has already released his tax returns, which Trump continues to stall despite mounting pressure, exacerbated recently by a report that he may have paid nothing for years.
In more ways than one, both VP nominees are very different from their respective running mates. Pence is sober, measured in his remarks, on the script and, to his fans, principled — unlike the flashy, free-wheeling, blustery, flip-flopping Trump.
Kaine comes across as folksy, spontaneous and trustworthy, where Clinton has been called scripted, robotic and generally untrustworthy — she and Trump have been polling record high numbers in unfavourability match-ups.
That's probably why they were picked.
But they will not get to talk about themselves, though it will be their only chance together on national stage, as much as about their running mates. Vice-presidential nominees, or their debate, don't determine the outcome.
"Don’t screw up — that’s the goal of a VP debate," Brett O’Donnell, a Republican communications specialist who advised prominent Republican nominees — including President George W. Bush, Senator John McCain and Governor Mitt Romney — told The New York Times.
As current and former governors, Pence and Kaine — of Indiana and Virginia, respectively — have plenty of experience of now screwing up, but they will be closely scrutinised for their defence of their running mates and how they explain differences and disagreements.
Pence will almost certainly be asked about Trump's refusal to release his tax returns and, more significantly, reports that he may have not paid taxes for years. Will he toe the party and call Trump a "genius" for doing that, as have surrogates such as Rudy Giuliani, the former New York mayor, and Chris Christie, the New Jersey governor?
There are difference between Pence and Trump, which the moderator, CBS News’s Elaine Quijano, will probe. Pence, for instance, has supported multi-national trade deals, which Trump rails against at every rally and political event.
Kaine will be probed on Clinton's emails, her family-run Clinton Foundation, her issues with untrustworthiness and foreign policy decisions from her term as secretary of state. But he is not expected to be tested as severely as Pence.
Memorable moments from past vice-presidential debates
As Republican VP nominee Paul Ryan unleashed his criticism of the Obama administration’s foreign policy, Vice-President Joe Biden, who is known for his casual, folksy manner, shot back: “With all due respect, that’s a bunch of malarkey.” An Irish-American word meaning nonsense, Biden, who is of Irish decent, went on to use it to rubbish criticism or attacks for maximum effect.
Republican Dan Quayle, who was running with George H W Bush, was answering a question about his experience or lack of it, saying President Kennedy, who had been elected as the youngest president while serving as senator, was just as qualified. Lloyd Bentsen, the Democratic nominee, told him, “Senator, I served with Jack Kennedy. I knew Jack Kennedy. Jack Kennedy was a friend of mine. Senator, you’re no Jack Kennedy.” That has become one of the most memorable lines from VP debates.