Tonight—and only tonight—belongs to Mike Pence and Tim Kaine. There is only one vice presidential debate, so the candidates have only one opportunity to prove their mettle before being forgotten, aside for the occasional gaffe, for the rest of the campaign.
Vice presidential debates are also useful in reframing, however briefly, presidential contests. In 2012, after a poor first debate for the Democrats, Joe Biden underscored the Obama campaign’s larger narrative—that Mitt Romney and Paul Ryan were emotionally detached vampire capitalists—by grinning repeatedly at Ryan. In 2004, Dick Cheney did something similar to John Edwards, who came across as callow and cheap next to the Vader-ish elder statesman. In both of these instances, the VP debates changed the narrative by taking attention away from candidates who were seen as struggling. Vice presidential debates can be palate cleansers.
But Donald Trump is not someone who is particularly comfortable with attention being paid to people who are not him. He broke from tradition earlier this year when he appeared on stage multiple times at the Republican National Convention. And on Tuesday night, he will do everything in his power to draw attention away from someone on his own team, even though drawing attention away from himself is exactly what his campaign needs:
Trump’s livetweets will almost certainly be bad and pointless. They will likely also have the added value of undermining his campaign.