Donald Trump has done some strange things to the Republican party. Gone is their disgust at Stalinist tyrants from North Korea. Vanished is their outrage at deficit spending. Evaporated is their horror at a president who ignores Congress and the constitution.

But those bizarre twists are nothing compared with the screwball comedy that was the House oversight committee on Wednesday, as its Republicans grilled Trump’s former fixer, henchman and bagman, Michael Cohen.

Because whether they knew it or not, Trump’s own party made the best possible case against Trump himself.

Amid all their righteous indignation on behalf of the truth, amid all their contempt for lies and the liars who peddle them, amid all their love of law and order, you couldn’t help wondering if they had ever heard of a man called Donald Trump.

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To be clear, the House Republicans thought they were doing a fine job for their Great Leader by trashing his former lawyer at every turn. Cohen is undoubtedly a proven liar who lied to Congress: we know this because he confessed to doing just that in his guilty plea last year.

Trump’s loyalists in the House seemed to think that was the end of the story. Who could believe a proven liar like Michael Cohen? The only snag is that he was lying on behalf of his client, one Donald Trump. So the more they talked about his lies, the more he talked about his lying client.

Play Video 1:28 Trump loyalists will 'suffer same consequences I’m suffering', says Cohen – video

Like so many things in Trumpworld, this line of questioning is several diopters worse than shortsighted. It is the kind of brilliant argument dreamed up after several beers: a bar-room brawl masquerading as political strategy.

The hapless Paul Gosar, an Arizona Republican, took a swing at Cohen but ended up falling off his stool. “Let’s go back at this credibility,” he bumbled after questioning Cohen’s legal credentials. “You want us to make sure that we think of you as a real philanthropic icon, that you’re about justice, that you’re the person that someone would call at three in the morning. No, they wouldn’t. Not at all … You’re a pathological liar. You don’t know truth from falsehood.”

“Sir, I’m sorry,” said Cohen. “Are you referring to me or the president?”

They should have seen this coming. Cohen opened the day’s fisticuffs by spelling out the lies at the heart of the matter.

“Mr Trump knew of and directed the Trump Moscow negotiations throughout the campaign and lied about it. He lied about it because he never expected to win the election. He also lied about it because he stood to make hundreds of millions of dollars on the Moscow real estate project,” Cohen said.

“And so I lied about it, too – because Mr Trump had made clear to me, through his personal statements to me that we both knew were false and through his lies to the country, that he wanted me to lie. And he made it clear to me because his personal attorneys reviewed my statement before I gave it to Congress.”

If the White House knew about Cohen’s lies ahead of time, what should Republicans say about his lying client?

This pesky problem led to plenty of moralistic psychobabble about the quality of Cohen’s repentance, the nature of redemption and the possibility of recidivism. The best cocktail of this type of Christian justice was shaken and stirred by Clay Higgins, a Louisiana Republican, whose previous career included several low-level positions in local law enforcement. Higgins was famous for talking tough to criminals on viral videos that landed him in trouble with his senior officers and the ACLU.

So there he was, bragging about the “several thousand men” he had arrested, wondering out loud if Cohen’s remorse wasn’t just another empty act before he returned to his old crooked ways. Because Higgins reckoned he would. Sniffing out the truth like the bloodhound of the law that he is, Higgins asked Cohen where he found that fateful check signed by Donald Trump to repay him for all that porn star hush money.

Cohen said he’d found it in a box in his old law office – a box that the FBI hadn’t seized. Bingo! Higgins solved the case. He urged the authorities to immediately seize the box and any other evidence in there.

This quite brilliant suggestion marked the high point, or possibly the low point, of Republican cluelessness. Higgins was literally asking the FBI to gather more evidence about Trump’s part in what is technically a five-year felony. Illegal campaign contributions are not small crimes for a candidate for high office. You might even call them a high crime, worthy of impeachment articles.

Cohen had a warning for the Republican stooges sitting in front of him. They were in danger of becoming just like him.

“I’m responsible for your silliness because I did the same thing that you’re doing now for 10 years,” he said. “I protected Mr Trump for 10 years.”

More than anything else, Tuesday’s hearing opened the lid on everything Trumpian the Republican party has kept under lock and key for the last two years.

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Harley Rouda, a California Democrat, asked about Felix Sater, the convicted Russian mobster, who enjoyed a rent-free office on the 26th floor of Trump Tower, down the hallway from the man who now sits in the Oval Office, according to Cohen. Alexandria Ocasio-Cortez, the star among New York Democrats, asked if Trump had inflated his assets to an insurance company. Jimmy Gomez, another California Democrat, asked if Trump was even being audited on his taxes – the supposed reason why the president hasn’t released his tax returns for public scrutiny.

With such perilous lines of inquiries and investigations ahead of them, Trump’s Republicans will soon need to ask some pretty tough questions of themselves. Just how long are they planning to protect the unprotectable?

“My loyalty to Mr Trump has cost me everything,” Cohen warned. “My family’s happiness, my law license, my company, my livelihood, my honor, my reputation and soon my freedom.”

It just wasn’t clear if he was talking about himself, or the Republicans who have surrendered more than they care to admit for Donald Trump.