Fox News political pundit Brit Hume offered a bleak forecast for presidential contender Joe Biden's campaign ahead of the Iowa caucuses on Monday.

"Biden, to me, looks like a guy who is wobbly on the ledge of a high building," Hume said. "And we keep expecting that he's going to go splat. And it hasn't happened yet."

Biden, a self-described "gaffe machine," has been overtaken in most Iowa polls by surging Sen. Bernie Sanders, who last week predicted he would win the first Democratic nominating content of 2020.

"I get in trouble when I say this, but I'm confident in a win here in Iowa," a Sanders campaign aide said.

"It'll be fun to watch him [Sanders] try to do it because, you know, the Democrats, obviously, they don't want to nominate Bernie Sanders," Hume responded.

Biden, a moderate Democrat in a shrinking 2020 primary field, is leading in most national polls for the Democratic presidential primary contest where a majority of voters have indicated an ability to beat President Trump is their top priority in selecting a candidate.