President Trump spoke at a news conference in Paris on July 13 and defended Donald Trump Jr.'s meeting with a Russian lawyer. (The Washington Post)

There’s a transition point that comes in many scandals when the facts make it impossible to sustain the argument the administration’s allies had been using. Specifically, it requires them to go from saying, “These accusations are false; it never happened” to saying, “Sure, it happened, but there’s nothing wrong with it.”

That is where Republicans now find themselves, and there’s a deep irony at work. Donald Trump rode into office on the widespread belief that politics is corrupt and only an outsider like him could clean it up. Now, it looks like his all-purpose excuse for his own misdeeds and those of his family and advisers will be, “Hey, don’t blame me — we all know politics is corrupt!”

You can see it in this tweet President Trump sent this morning:

As numerous politicians and political professionals from both parties have attested since the story of the meeting between Don Jr., Jared Kushner, Paul Manafort and a group of Russians who were explicitly presented to them as acting on behalf of the Kremlin, that’s not just untrue but absurd. When a hostile foreign government offers you help in your campaign, what you do is call the FBI.

The idea animating Trump’s position is that during a presidential campaign there is virtually no sin or even crime that can’t be justified on the grounds that, well, it’s a campaign. As Fox News personality Jeanine Pirro said in defending Trump, “As someone who’s run for office five times, if the devil called me and said he wanted to set up a meeting to give me opposition research on my opponent, I’d be on the first trolley to Hell to get it.” Or in the words of Sean Hannity, “It always happens. And if anyone says it doesn’t, it’s a lie.”

So having spent months claiming that the accusation that the Trump campaign colluded with the Russian government in its attempt to swing the election to Trump was ridiculous, now their position is that there’s nothing wrong with collusion. Forget it, Jake. It’s Chinatown.

This can become a handy excuse for almost anything. Did Trump fire FBI Director James B. Comey to shut down the Russia investigation? It’s politics! Is Trump using the office of the presidency to enrich himself and his family? It’s politics! Having convinced his supporters that Washington is an irredeemable swamp of corruption that he will clean up, Trump now holds himself blameless for any malfeasance, because look at what a swamp this place is.

The people who actually have experience in politics agree that there are ethical limits to what you may do in pursuit of your political goals. But Trump, believing his own caricature of what politics is, feels constrained by no limits whatsoever. He approaches governing as though it were professional wrestling, not something with any substantive meaning but a series of staged fights you perform so your side cheers. Sure, there are “rules,” but they’re no more important than the rule that you’re not supposed to hit your opponent with a folding chair. If it’s part of the show, you do it.

In the context of that show, there’s no such thing as a political opponent with whom you still share some things in common, like a commitment to the country’s founding ideals. There are just enemies, and the war against them has to be total. If Russia wants to help you fight your true enemy (Hillary Clinton), then you welcome the help.

The Post's Ruth Marcus explains why Donald Trump Jr. is in legal jeopardy. Hint: stupidity is not a legal defense. (Adriana Usero,Kate Woodsome/The Washington Post)

And there are a certain number of Trump’s supporters for whom the fight is its own reward, just as his 2016 campaign was its own reward even before he won. It was thrilling and liberating, allowing them to stop hiding their thoughts and give vent to their feelings, no matter how “politically incorrect” they might be. No need to worry anymore about some liberal calling you racist or sexist — just put on your “Trump That Bitch” T-shirt, tell somebody with a Spanish accent what you think of immigrants, and let it rip. Who cares if he actually accomplishes anything on policy or makes anyone’s life better? As one Republican voter tells the Des Moines Register, “I just want him to annoy the hell out of everybody, and he’s done that.”

Just to be clear, there are Republicans criticizing the Don Jr./Jared/Manafort meeting and no doubt dreading what the next revelation will bring. Trump’s approval is down to the mid-30s, and when the latest Post/ABC News poll asked about the meeting, only 48 percent of Republicans said it was appropriate, hardly unified support for the White House’s position.

There’s obviously a great risk for Trump and his allies in using the “It’s politics” defense. As pollster Guy Molyneux recently explained in the American Prospect, while we use the word “populism” to describe both Trump’s appeal to working-class voters and that of Bernie Sanders and Elizabeth Warren, unlike those Democrats Trump made an argument focused not on economic elites but on politicians and “Washington,” and his voters responded. But he’s now saying that he’s no different from any other politician, and the people he brought with him (including his own family) are simply adopting the mores and standards of Washington.

Even if that excuse were to fly, it wouldn’t leave him a lot of room to claim in 2020 that he had transformed politics, drained the swamp and fulfilled the promise of his 2016 campaign. Most of his supporters might decide that it’s enough for him to have the right enemies. But they may not be as excited to get out to the polls again if he keeps telling them that what he does is just politics.