In 2015, I started to set fire to my good standing on the right because I believed—and still believe—that the arguments and tactics gaining hold on the right would do lasting damage to both conservatism and the country. I see something similar happening on the left.

Now, I should pause and say that labels are complicated here, because there are many factions that fall under the rubric of the “New Right,” and they are not all the same. There are nationalists who aren’t post-liberals, and there are post-liberals who aren’t nationalists—or even Trump fans. Many on the New Right despise the Nick Fuentes crowd, while others seek its approval. You can’t lump them all into the same category without being unfair to some of them.

But what broadly—if not uniformly—united this populist popular front of rightists in 2015 and 2016 was a varying degree of tolerance for some truly terrible people and ideas. Under the flag of people like Steve Bannon, the “alt-right” was sanitized as a faction of the broader Republican or Trumpist coalition, while people who didn’t want to be part of a movement that included such people were anathematized as “RINOs” and bedwetters. That’s what popular frontism is: a willingness to accept anyone on “your side” who hates the “other side” more, and an unwillingness to put up with people who have a problem with popular frontism.

I would get lectured during that campaign cycle about making too big a deal out of neo-Nazis, neo-Nazi apologists, Pizzagate and Sandy Hook truthers, and general sleazeballs like Roger Stone. We need to unite against Hillary, they’d say. A lot of good and decent people—a few still friends of mine—adopted the view of, “Yeah, these are terrible people, but the times require an anti-anti-terrible people stance.” At least the terrible people “know what time it is.”

I’ve been wrong about a great many things in the last eight years, but I was right for rejecting all of that garbage. The idiotic speakership drama is just the latest evidence that the GOP is no longer a party united around conservative principles. Sure, it is still home to most conservatives, but the loyalty tests now have little to nothing to do with conservative commitments. Today you can be a diehard constitutionalist and social conservative, but if you don’t like Trump, you’re a “RINO.”

Today’s left is obviously extremely different in a number of ways, but it’s hard not to see a similar dynamic playing out in front of our eyes. The primary reason so many conservatives twisted themselves to the new reality of the Trump era was that it was in their short-term political interests to go with the herd. Trump was popular. So how can you expect a politician—or media personality dependent on the same audience—to say his or her customers are wrong?

This is one of the key dilemmas presented by both democracy and populism. It is very easy to condemn bad ideas when bad ideas aren’t held by very many people. But when bad ideas become popular among the broader public—or among a sizable enough faction of a narrower coalition—the holders of those ideas stop being “wrong” and start becoming “a constituency.” This is an even bigger problem in a country where both parties have little to no interest in winning over voters outside their coalitions. If every election is a base election, then the last thing you can do is piss off anyone in your base.

Election-deniers on the right are wrong, full stop. But there are a lot of them. So even Republicans who know better have to pretend it’s all so very complicated. The full-bore anti-vaxxers are wrong. But you can’t say so without inviting more headaches, so Republican politicians—including Trump himself—play word games to avoid offending the crowd that thinks that anyone who died of a heart attack was killed by Pfizer. I think Trump is manifestly and obviously unfit for office, and whether you disagree with me or not is immaterial to my point. A great many Republican lawmakers agree with me—including many of the Republican politicians running against Trump in the presidential primary—but few can bring themselves to say so publicly.

Now of course, this has always been part of politics. Politicians have always parsed, evaded, trimmed, and hedged on various issues that divide their coalitions. But not all issues are equal; some are corrupting if you compromise on them. Liberals in the 1940s and 1950s realized this when it came to the problem of domestic communism. They eventually recognized that playing footsie with communism wasn’t merely wrong, it was suicidal for Democrats, for liberalism, and, if appeased long enough, possibly for the country. That’s how Americans for Democratic Action was born. Slavery played a similar role, first for the Whigs and ultimately for the nation. A house divided and all that.

I think the conspiracy theorizing, cult-of-personality garbage, and post-liberal nonsense play similar roles for the right. I don’t mean to say they are equal to the threat communism posed or as morally freighted as slavery, but if left unchecked, they pose profound, even existential, threats—to conservatism certainly, and to the country potentially. There are, for instance, a small number of New Rightists who bleat and prattle about civil war, national divorce, or secession. Their numbers, in my opinion, are as low as their patriotism and their IQs. But if such ideas were allowed to grow unchecked, the dangers are obvious. I don’t think those ideas will be allowed to spread unchecked for myriad reasons, not least because Donald Trump won’t live forever. But that’s all a conversation for another time. I think you get the point.

The split we see on the left poses similar problems for liberalism and the Democrats. For starters, the intellectual left has a lot more post-liberals in it than the right does, and the left’s post-liberals have much better perches. A lot of them have tenure. But the more relevant point is that the left cannot endure as a coherent movement with a faultline like the one we see opening up before us.

For the same reason that I, a politically conservative secular Jew, did not want to be in a popular front alongside people who would routinely tell me that they wished Hitler had taken care of the job of putting my grandparents in an ashtray, I don’t think many liberal Jews will want to remain in a popular front with apologists for butchering Jewish babies and raping Jewish women. The point isn’t that most—or even many—people on the left believe any such things. The point is that even having a “big tent” that includes such a minority is both untenable and corrupting. I expect to see Democratic politicians play the same games we’ve grown familiar with from Republicans. Some Hamas apologist like Rep. Rashida Tlaib will tweet something awful, and Democrats will say, “I haven’t seen the tweet” when we know they have.

There’s plenty of room for criticizing Israel from the right or the left. And both parties have long included factions that fall along a relatively broad spectrum of support or opposition to Israel. But a moral and political law of the excluded middle applies when it comes to butchering babies, never mind butchering babies solely because they’re Jews. Either you think it’s entirely and wholly evil and unacceptable or you don’t. You can’t build a coalition, at least not an enduring one, that makes room for both sides.