Republicans have bet their future on the proposition that character does not matter, or at least not the character of Donald Trump.

So, perhaps too late, they are discovering that having a president who is a chronic liar is both morally and politically problematic. As a New Yorker, Trump is surely familiar with the hoary adage that “the fish rots from the head down.” As president, he has turned it into a governing principle.

The consequence is that Republicans now face a midterm election that is likely to turn less on tax cuts than on the miasma of sleaze and corruption that surrounds them.

Until now, Republicans have been able to comfort themselves by pointing to policy wins, a strong economy, and a political culture in which nothing matters. And maybe nothing does. But this feels like a turning point of sorts. This week was the worst of Donald Trump’s presidency. But it seems likely there will be worse still.

On a single afternoon, Trump’s former campaign manager, Paul Manafort, and his personal attorney, Michael Cohen, became convicted felons and the president himself was implicated in the illegal payment of hush money to a porn star and a Playboy Playmate.

The significance of this cannot be overstated. For the first time, the president has been tied directly to a criminal act. If Trump knew about the payments in advance, noted former Department of Justice official Harry Litman, “he’s looking at liability as a conspirator for what is now a proven crime.” Or as Cohen’s new lawyer, Lanny Davis, asked with unwonted reasonableness: “If those payments were a crime for Michael Cohen, then why wouldn’t they be a crime for Donald Trump?”

The stain is also spreading.

Within hours of Manafort’s conviction and Cohen’s plea, one of Trump’s earliest congressional supporters, California Representative Duncan Hunter was indicted for misusing $250,000 of campaign money for personal use and filing false campaign finance records with the Federal Election Commission. The charges came a few weeks after the indictment of another early Trump supporter, New York Representative Chris Collins, for insider trading.

The 60 count indictment against Hunter and wife detailed a remarkable pattern of greed and grifting including using campaign cash to pay for airfare for a pet rabbit, 30 shots of tequila, and “buying personal clothing items at a golf course so that the purchase could be falsely reported to the Treasurer as ‘balls for the wounded warriors'."

But the day before his arraignment, Hunter was defiant, explicitly tying himself to Trump. “This is the new Department of Justice. This is the Democrats’ arm of law enforcement, that’s what’s happening right now,” Hunter told a local television station. “It’s happening with Trump, and it’s happening with me.” (Actually, the DOJ is run by Republicans, appointed by Trump, but maybe Hunter was hoping to be taken seriously, not literally.)

Unfortunately for the GOP, this spreading stink of corruption has a cumulative effect, and the threats to Republicans seem to be intensifying almost daily. The Manafort verdict was a huge vindication for Robert Mueller’s investigation, even if it did not directly address charges of Russian collusion. Cohen knows details of Trump’s operation and appears anxious to unburden himself to prosecutors. Other Trump intimates are also cooperating with the probe, including White House counsel Don McGahn.

None of this is going away and it is likely to get worse. And perhaps the greatest immediate danger to Trump is . . . the president himself.

When he’s cornered, Trump’s instinct is to lash out, but as Jack Goldsmith has pointed out, the president could do more than rage on Twitter. He could go nuclear, by firing the special counsel or the leadership of the Department of Justice, or stripping more officials of security clearances, or deploying his virtually unlimited power to pardon.

Such steps would ignite a political firestorm and a constitutional crisis. But none of them seem far-fetched for a president so unmoored to prudence, much less to democratic norms or the rule of law.

The morning after Manafort’s conviction on eight felony counts, Trump tweeted out praise for his refusal to “break,” by cooperating with prosecutors. “Such respect for a brave man!” the president of the United States wrote of a man who faces 80 years in prison for committing federal crimes and defrauding the U.S. government.

In tone and substance, Trump sounded more like a mob boss than an occupant of the office once held by Abraham Lincoln. But in GOP circles, it merited scarcely a raised eyebrow. Whether because of cowardice or cynicism, Republican leaders have made their peace with Trump’s swamp.

Unfortunately for the GOP, that may be the fatal legacy of Trumpism.

Trump (and his many imitators) know that they can count on a supine party and sycophants in the conservative media to deflect or rationalize pretty much anything. It helps that there is an apparently infinite appetite for reputational self-immolation among Trump defenders.

Just as dangerous is Trump’s effect on others in his orbit who seem to have absorbed his arrogant amoralism and the smug conviction that they are immune from consequences.

Having convinced themselves that nothing matters, Republicans have encouraged the notion that they can get away with pretty much anything because their tribal allies will always provide them cover. The consequence has not only been an extraordinary tolerance for deception, corruption, and cruelty, but an embrace of a free-floating moral relativism that is wholly alien to the traditional notions of conservatism.

The congressional GOP is not simply collateral damage here. Their own invertebrate quiescence has not simply enabled Trumpism’s worst and most dangerous instincts, but actually has encouraged them.

Under Trump, the GOP is not merely tolerating swampiness, it has created the ideal, fetid environment for growing and multiplying swamp creatures. Worse, Trumpism has seemingly robbed Republicans of the capacity to confront the moral rot they have helped create. No GOP senator seems eager to play the role that Senator Howard Baker played in Watergate. There are no Barry Goldwaters willing to tell the president hard truths.

Of course, there may still be time for conservatives to remember who they used to be and what they used to believe. But if they fail to do so, they will lose more than an election.