Trump lawyer-turned-betrayer Michael Cohen took a detour on his way to prison with a lovely day trip to Washington and a televised sitdown with the House Oversight Committee.

He spent much of his time savaging the president unmercifully, which earned him savage treatment of his own from the Republican members of the committee and strange new ­respect from members on the other side of the aisle.

I haven’t heard that much histrionic and annoying yelling since I had the misfortune to have the batteries run out on my remote control while the channel changer was stuck on the Samantha Bee show.

The weird thing: Since what Republicans were trying to do was save the president’s hide, they should actually have hoisted Cohen on their shoulders, sung “Hava Nagila” and done a nine-hour hora. His testimony and answers actually helped the president when it came to the matter of Trump’s possible impeachment.

It turns out his lawyer-fixer doesn’t have the goods.

Early reports on what Cohen might say suggested he was ­going to tell the committee that Trump told him to lie to Congress about his alleged porn-star payoffs. That would have meant the president had suborned perjury — a serious crime. Such testimony would indeed have amounted to a smoking cruise missile aimed directly at the White House.

But that is not what Cohen said.

This is what he said: “Mr. Trump did not directly tell me to lie to Congress. That’s not how he operates. In conversations we had during the campaign, at the same time I was ­actively negotiating in Russia for him, he would look me in the eye and tell me there’s no business in Russia and then go out and lie to the American people by saying the same thing.” Cohen added: “In his way, he was telling me to lie.”

If a president is to be ­impeached when an associate says he intuited that the president wanted him to lie under oath, there is no president following Trump who wouldn’t be ­vulnerable to the same charge and to impeachment under the same standard.

That is why subornation of perjury has a high evidentiary standard and one that mustn’t be lowered just because liberals and Never Trumpers are determined to see Trump ­humiliated.

Cohen may be right that Trump wanted him to lie, but without having issued a direct order that Cohen do so, Trump can’t properly be charged with the offense. If he is guilty, he is guilty in exactly the manner that the vicious gossip columnist J.J. Hunsecker is guilty in the great New York melodrama “Sweet Smell of Success” — getting others to do his dirty work without leaving a trace.

“My right hand hasn’t seen my left hand in 30 years,” J.J. says.

Also significant is the fact that Cohen said flatly, as he had said repeatedly in 2016, that he hadn’t traveled to Prague to meet with Russians, a key allegation in the sleazy “Steele dossier” full of uncorrobated ­rumors about Trump as a Russian asset.

He did say he had his suspicions that Trump knew more about the meeting in Trump Tower with a Kremlin asset in June 2016, but had no evidence of anything untoward.

He also said he had pursued a supposed tape of the president striking his wife Melania in a Moscow elevator to buy it and destroy it and became convinced there was no such tape, nor did he believe that Trump would engage in such behavior. He said he had sought information about a supposed Trump “love child” but became convinced that story was false, too.

And as for the infamous ­so-called pee tape, Cohen told Rep. Jamie Raskin, “I’ve had many people contact me over the years. I have no reason to believe that that tape exists.”

Cohen did say Trump was a racist and a con man and a liar and disloyal and awful in a million different ways. It was a very, very bad day for the president. If there is anyone in this country or on this planet still on the fence about Trump’s character, Cohen’s testimony likely sealed the deal on that question.

But congressional Democrats didn’t get what they needed from Cohen to pursue impeachment in a manner that won’t seem simply like a hyper-politicized sop to the haters.

jpodhoretz@gmail.com