John Minchillo / AP

Give the fourth Democratic presidential debate its due: Yes, it was interminably long, but it was also terminally boring.

There are several reasons the debate never really took off, but the central problem was that each of the candidates is seeking to excite the Democratic base, and right now the thing that is most exciting to Democrats is impeaching Donald Trump.

This led to a disorienting evening. There’s a strong likelihood that at some point between now and November 2020, the House of Representatives will impeach the president of the United States, and yet the debate was barely different from the three that preceded the start of a serious impeachment inquiry in late September.

Although the first question of the night focused on impeachment, the moderators and candidates quickly moved on, barely mentioning it over the rest of the three hours of debate. In those opening moments, Senator Amy Klobuchar defended the inquiry against charges that it’s a distraction.

“We can do two things at once,” she said. “That’s our job. We have a constitutional duty to pursue this impeachment. We also can stand up for America, because this president has not been putting America in front of his own personal interests.”

True enough for Congress, perhaps, but the candidates are in a tougher spot. All of them support at least an impeachment inquiry, but there’s not much else they can say. They are all trying to beat him in an election that would moot an impeachment. Yet any impeachment proceedings will conclude by the time the presidential election happens, and if Trump were to be removed from office, which still seems very unlikely, it would be outside the candidates’ control.

Impeachment isn’t the only reason that tonight’s debate was a bit of a bust. First, there are simply too many candidates. People moan about two-night debates, and they groan about not having the leading trifecta of Elizabeth Warren, Joe Biden, and Bernie Sanders together onstage. But this meeting showed how pointless it is to cram all 12 candidates into one night. The moderators were reasonably effective within the bounds they were given, but no debate this large is structured to allow meaningful debate or exchanges. Even middle-tier candidates got lost for long stretches at a time. Tom Steyer, in his first appearance, found that money could buy him onto the debate stage, but it couldn’t buy him questions or attention.

Second, the candidates agree on most issues. Remember the old line about how academic debates are so bitter because the stakes are so low? The few moments of drama in this debate were high because the policy differences are so narrow. There were a few flare-ups on the stage tonight, mostly between Warren and would-be challengers (though Pete Buttigieg mixed things up with both Beto O’Rourke and Tulsi Gabbard). But by and large, the candidates agree: Trump is bad, his withdrawal from Syria is disastrous, more gun restrictions are needed, abortion rights should be protected, climate change is a threat, and so on.

They disagree on a few areas, with health care being the most notable and important—though even there, the gap between, say, Buttigieg and Sanders isn’t that big: Both Medicare for All Who Want It and Medicare for All would be major transformations of the system. Moreover, these differences have been worked over extensively in each debate so far. Warren even got the same question about whether she’d increase taxes to pay for health care that she’s gotten in the previous debates; to no one’s surprise, she once again sidestepped the question, saying total costs would go down.

Besides, the areas where the candidates do substantially disagree are also largely areas where the candidates are unlikely to have much real muscle to execute their plans. Any Democratic president would probably be lucky, and grateful, to get to Medicare for All Who Want It.

Most of these factors have been present in past debates, but impeachment was the elephant in the room tonight: the dominant story in national politics, and yet quickly dispensed with on the debate stage. It’s an unsolvable problem for Democratic candidates. A presidential-primary debate is normal, and impeachment is not, and it’s incoherent and disorienting for them to be proceeding at the same time. If Trump is impeached but not removed, it will probably, as David Leonhardt writes, aid whoever ends up as the Democratic nominee. For the time being, though, campaigning while impeachment proceeds is a conundrum that relegates the candidates to sideshow status.

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