IT’S EXHAUSTING being both a conservative and a critic of President Trump. When I aim my pen at the White House, many of my comrades on the right go nuts. And readers who love it when I go after Trump turn into a cage full of poo-flinging monkeys when I turn my attention to the Democrats.

So let me try to head things off at the pass and say that, yes, the President is inexcusably contemptuous of constitutional norms and the basic processes of our system. He is transparently ignorant on these matters, possessing a thumbless grasp of basic civics.

With that out of the way, I have a question: What is Elizabeth Warren’s excuse? Or Kamala Harris’? Or Bernie Sanders’? Or Beto O’Rourke’s?

Take Warren. She was a Harvard law professor and prizes her reputation as a very serious policy wonk. And yet vast swaths of her proposed agenda are either illegal or unconstitutional. For instance, she has vowed to implement a total ban on fracking once she’s elected. The only problem: The President doesn’t have that power. Congress passed a law in 2005 giving wide latitude to states to allow fracking. The Obama administration tried to circumvent the Energy Policy Act — in a far less audacious way than Warren’s plan — and the courts slapped it down. In short, Warren is promising something illegal.

Warren’s wealth tax is almost surely unconstitutional. So is her plan for creating a national statutory right for abortion. As National Review’s David French (a former Ivy League law professor as well) recently detailed: “Time and time again, the pattern is the same. She’ll push regulatory authority beyond the statutory limit. She’ll push statutory authority beyond the constitutional limit. In so doing, she’d represent the next stage in imperial presidential evolution — reaching beyond both President Obama and President Trump, two men who have had their own problems staying within their constitutional boundaries.”

But forget about the legal and constitutional niceties and just focus on the politically possible. Like President Trump, most of the Democratic contenders say they want to get rid of the legislative filibuster, making Senate Majority Leader Mitch McConnell a more responsible steward of the constitutional order. And nearly all of the radical proposals they support — from gun control to “Medicare for All” to the Green New Deal — are politically impossible without doing so (and probably impossible even without the filibuster). But no one explains how they could accomplish such a repeal.

To his credit, Sanders doesn’t want to get rid of the filibuster. He just claims he could socialize medicine through the budget reconciliation process. He can’t.

Then there’s math. Nearly all of the grandiose plans to socialize medicine and fight climate change would require massive tax hikes. But Warren, who won’t say she’ll raise taxes on the middle class, insists that the rich can pay for it all. They can’t. You could literally (and unconstitutionally) confiscate all of the wealth of the top 1 percent and it wouldn’t cover the Green New Deal alone, by some estimates.

A majority of Americans are concerned about climate change. But when the issue moves from virtue-signaling to actually paying for it, they blanch (as Australian voters recently did). According to polls, a majority of Americans are unwilling to spend more than $24 a year on electricity to combat climate change.

Indeed, I think virtue-signaling explains much of what is going on. None of these sweeping promises have any chance of surviving contact with Congress, never mind the voters. But that’s beside the point. The Democratic primary is an emotive contest to prove who cares the most.

Last week, when Joe Biden noted, rightly, that sweeping gun bans by executive order would be unconstitutional, Kamala Harris replied, “I would just say, hey, Joe, instead of saying, ‘No, we can’t,’ let’s say, ‘Yes, we can.’” When she was done giggling at her own quip, she didn’t provide an argument; she demagogued on the issue by pointing to the victims of gun violence, in much the same way President Trump uses the victims of criminals who are in the country illegally to support his constitutionally dubious border plans.

One of the reasons our politics are so ugly is that politicians and activists insist the impossible is not only possible, but easy. When the inevitable failure materializes, the same politicians blame it on nefarious special interests and a rigged system. This, in turn, leads not just to more cynicism but a desire for leaders who will tear down everything, the Constitution be damned. That’s how we got Trump, and that’s how we got this execrable field of virtue-signaling Democrats.

Jonah Goldberg’s latest book, “Suicide of the West,” is now available wherever books are sold.