Are Democrats becoming extremists?

That’s not to say that the Resistance and the Democratic Party are working in tandem. Indeed, what’s happening carries real risks for the Democrats: In yet another parallel with the Tea Party, the Resistance is fighting against its own party’s leaders as well as the opposing party. We saw this in the replay of the Bernie Sanders-Hillary Clinton 2016 primary spat in this year’s race for chair of the Democratic National Committee, with Keith Ellison playing the role of Sanders and Tom Perez standing in for Hillary Clinton.

Just as the Tea Party pushed the GOP toward obstructionism and ideological rigidity, the Resistance is starting to force the Democratic Party toward its extremes and away from long-held norms of bipartisan give-and-take. Resisters threaten Democratic politicians with terrible retribution if they vote in favor of any of Trump’s nominees or major Republican legislation, regardless of merit. As a result, Democratic officeholders have less and less to say about the value of compromise, seemingly fearing that anything they say will be seen as “normalizing” and “legitimizing” the Trump presidency.

Odds are growing that 2018 will see a rash of Resistance-driven primary challenges to centrist Democrats. Privately, the party’s professionals dread a repeat of what has happened on the Republican side, when successful center-leaning politicians lost low-turnout primaries to fringe candidates who went on to crashing defeat in the general election. (Think of Indiana Senator Richard Lugar losing the 2012 primary to Richard Mourdock, who then went on to lose to Democrat Joe Donnelly.) It’s not hard to imagine an Elizabeth Warren-style challenger upsetting Sen. Joe Manchin in the West Virginia Democratic primary in 2018, but that liberal victor would face long odds in a state where Trump took nearly 70 percent of the vote in 2016. The impulse to primary moderates from your own party is real and has a certain appeal, but those victories are often Pyrrhic, forfeiting long-term success for short-lasting gratification.