“A big question now is, can Warren and Buttigieg avoid the Dean-Gephardt murder suicide pact?” said Steve Elmendorf, who advised Gephardt in 2004.

“There’s always a risk in any campaign, when two candidates go after each other and go after each other hard, it lets a third or fourth candidate rise because voters get sick of the attacks,” added Elmendorf, who favors Buttigieg, the mayor of South Bend, Ind. “In 2004, it was a big back and forth between Dean and Gephardt, and Kerry rose from behind and just ran up the middle and surprised everyone.”

So far, Warren and Buttigieg have been tamer in their attacks than Gephardt and Dean were in 2004, when they blasted each other repeatedly by name and in TV ads, Elmendorf said. The post-Christmas ad blitz expected from the Warren and Buttigieg campaigns will show whether that holds.