That’s the Democratic Party today. Beating Trump depends on finding a candidate who can galvanize all of these disparate factions. The Democrats need, all at once, to get white Midwestern conservatives to return to the party after they either switched to Trump or stayed home in 2016, and inspire a level of enthusiasm among black voters that approaches what they felt when Obama was running, and keep white urban and suburban liberals engaged enough that they both show up to vote for the party’s nominee a year from now and refuse to back a third-party candidate from the socialist left if Biden gets the nomination or one from the plutocratic center if Sanders or Warren do.

If that sounds impossible, that’s because it may well be — at least without a once-in-a-lifetime political talent like Barack Obama at the helm, willing and able to bring this fractious, wildly diverse, quite possibly incoherent party together. Having a widely despised Trump provoking the party every day will help. But there’s very little reason to think that negative partisanship will be sufficient. That’s because certain factions of the Democratic electoral coalition fear and loathe other factions of their own party almost as much as they fear and loathe the Republican president.

Unless and until that changes, the Democrats will find it more difficult to prevail than one might be led to suspect from looking solely at the persistent and deep unpopularity of the man they will be facing next November.