3. Biden’s other rivals haven’t even tried to compete for moderates’ support. At the outset of the campaign, few of Biden’s chief rivals even tried to compete for the moderate vote. Harris repeatedly embraced single-payer health care until she realized it was a political loser. Her new plan still phases out private health insurance, but after 10 years. Beto O’Rourke, once seen as a charismatic pragmatist, is now calling for mandatory confiscation of assault weapons. Cory Booker and Pete Buttigieg played to the base early on, before recalibrating their messages as they struggled to build momentum.

Of the 10 candidates on the debate stage, only Biden and Amy Klobuchar have consistently run as pragmatists, resisting the most ambitious progressive proposals.

Biden is winning 41 percent of moderate Democratic voters, according to last month’s Quinnipiac poll. If that advantage endures heading into the Iowa caucuses, he will be tough to beat.