Many of the prominent Republicans showing up at the Manhattan Criminal Courthouse appear to be motivated by ambition: They want to be Donald Trump’s running mate, and they’re hoping the gesture of support will impress the former president.

House Speaker Mike Johnson, however, doesn’t appear to have any interest in his party’s vice-presidential nomination. Rather, the Louisiana Republican made the trip to New York City yesterday to engage in a raw partisan display. As the Associated Press noted, Johnson became “the highest-ranking Republican to show up at court, embrace the former president’s claims of political persecution and attack the U.S. system of justice.”

It was a remarkable moment in modern American politics: The House speaker amplifying Trump’s defense and turning the Republican Party against the federal and state legal systems that are foundational to the U.S. government and a cornerstone of democracy. Johnson, who is second in line for the presidency, called the court system “corrupt.”

The display was, by any fair measure, obscene. The sitting speaker of the House — Congress’ top official and a man two heartbeats from the presidency — decided that it would be fully appropriate to show up at a criminal trial and allow himself to be used as a mouthpiece for a suspected felon.

Johnson could’ve stuck to a relatively anodyne script, telling reporters that he expects his party’s presumptive 2024 nominee to ultimately be exonerated, but the GOP leader went far further, lashing out at the judge in the case, prosecutors, witnesses and even the system itself.

The broader context didn’t do the House speaker any favors: Johnson, a man who is largely defined by his Christian faith and socially conservative principles, was putting his credibility on the line in defense of a man who stands accused of falsifying business records in order to cover up illegal hush-money payments to a porn star — whom Trump allegedly had a sexual encounter with while cheating on his third wife (a claim that Trump has denied).

Or as Democratic Rep. Jamie Raskin told the Daily Beast, “I don’t find anything unusual about a fundamentalist theocrat who thinks the Bible is the supreme law of the land attending the legal proceedings of an adjudicated sexual assailant and world-class fraudster and con-man for cooking the books to cover up hush money payments he made to a porn star to conceal his adulterous affair. Do you?”

What’s more, the public relations gambit looked even worse after Johnson’s political operation turned his appearance in New York into a fundraising appeal.

But perhaps most notable of all was the House speaker’s comments about his plans for the near future — because as it turns out, Johnson intends to use his courthouse appearance as a springboard toward future action. The conservative Washington Times reported:

House Speaker Mike Johnson … told reporters that all the cases brought against Mr. Trump amount to election interference and Congress has a constitutional responsibility to investigate the prosecutors and “hold them accountable.”

In fact, Johnson accused special counsel Jack Smith of undefined “abuses,” adding that he’s prepared to take measure to “rein in” prosecutors that Republicans disagree with.

It’s possible, of course, that the Louisianan was just peddling hollow rhetoric, and he won’t actually follow through on this in any meaningful way.

But even the possibility that Johnson intends to interfere in ongoing criminal cases, going after prosecutors for their doing their jobs and following the evidence, is a case study in indefensible Republican radicalism.