Julian Zelizer is a professor of history and public affairs at Princeton University and author, with Kevin Kruse, of the new book "Fault Lines: A History of the United States Since 1974." Follow him on Twitter at @julianzelizer. The opinions expressed in this commentary are his own. View more opinion at CNN.

(CNN) Bill Maher closed his show on Friday night with a warning to Democrats: "All the Democrats have to do to win is to come off less crazy than Trump — and, of course, they're blowing it, coming across as unserious people who are going to take away all your money so migrants from Honduras can go to college for free...."

Julian Zelizer

While Maher admitted he wasn't particularly enthusiastic about Joe Biden, he reminded viewers that the former Vice President is the only Democrat who can beat Trump in Ohio . Comparing him to non-dairy creamer, Maher joked, "nobody loves it but in a jam it gets the job done."

Maher captures the essential promise of the Biden campaign: he can win against Trump. Never mind the lack of excitement among many voters, or the struggle to concisely articulate what his campaign is about, this thinking goes. He might not be a perfect politician, but a Biden presidency would be better than a another four years of President Trump.

This is the big bet that many Democrats are willing to make as they double down on a candidate who has delivered a less than stellar performance thus far. Facing an incumbent president with relatively strong economic numbers and united party support, Biden Democrats are hoping to beat the odds and make Trump a one-termer in the tradition of Herbert Hoover, Jimmy Carter and George H.W. Bush.

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