The Joe Biden polling surge has raised the frightful specter of Democratic rationality.

What if Donald Trump hasn’t driven Democrats insane, sending them into a spiral of self-defeating radicalism, but instead made them shockingly pragmatic?

Biden’s early strength suggests it may be the latter, that the reaction to Trump is so intense that it has crossed some sort of event horizon from fevered fantasy of his leaving office early via resignation or impeachment to a cold-eyed, win-at-any-cost practicality.

If this is true, one of the exogenous factors that could appreciably increase Trump’s odds of reelection — a zany Democratic nomination contest leading to a nominee much too far left for the American electorate — may not materialize.

The commonsense play for the Democrats has always been to nominate a nonsocialist with appeal to Obama-to-Trump voters in former Blue Wall states — if not necessarily Biden, then someone with a similar, relatively moderate profile.

If hardly dispositive, Biden’s robust numbers at least suggest that this play is more likely than it seemed in the very early going, when candidates were stumbling over one another apologizing for sundry alleged offenses in the Woke Olympics.

If that’s not going to be the true dynamic of the race, I’m as surprised as anyone. What’s extraordinary, though, is that almost every Democratic candidate might have been misreading it as well, and chasing the wrong rabbit down the track.

Certainly, Bernie Sanders dominated the intellectual and policy debate in the wake of his 2016 run, driving other presidential candidates to embrace his signature proposals. And Alexandria Ocasio-Cortez is a genuine political star.

It’s only because the center of gravity of the party has clearly moved left that Biden, always a standard liberal, now sounds like a centrist when he calls himself an Obama-Biden Democrat.

But, as Harry Enten of CNN, among others, has been insisting for some time, the average Democrat is older, more moderate or conservative, and less likely to have a college degree than you’d guess from following Twitter or cable TV.

These voters were underserved by the rest of the field, and Biden is taking dead aim at them with the simple message that he can beat Trump.

Electability is usually a wan, uninspiring rationale for lackluster establishment campaigns, but Trump may have transformed into something more urgent and exciting for Democrats in 2020.

In this scenario, fear and loathing of Trump doesn’t drive Democrats into a politically risky dead end like impeachment — although that’s still possible — but a sensible appraisal of how to beat him at the ballot box.

In a recent CNN poll, about half of Democrats said it’s “extremely important” that a candidate have a good chance of beating Trump, much higher than any other candidate quality. Journalists on the trail have reported hearing the same thing from Democratic voters.

Of course, if we learned anything from 2016, it’s that pundits know much less about electability than we think. Biden’s paper strength may dissipate.

How often in American politics has the old candidate promising a restoration won? History shows that Democrats have had better electoral luck when they fall in love with a youthful candidate promising a fresh start. Think Bill Clinton, not Walter Mondale; Barack Obama, not Hillary Clinton.

Biden’s long record has plenty for Trump to shoot at, and after he gets beaten up over his past positions on busing and crime, he may have some of the same trouble as Hillary turning out the Democratic base.

Biden’s electability will have to be proven not just in general election polling matchups with Trump, but day-by-day campaigning during the primaries with more incoming than he’s experienced to date.

All that said, Biden’s level of support out of the gate has already changed the narrative of the race. It may be that he’s understood how Trump is shaping the 2020 landscape better than his more with-it and current Democratic competitors.

© 2019 by King Features Syndicate