The first presidential debate on Monday wasn’t short on acrimony, but as The Daily Beast’s Michael Tomasky noted,Hillary Clinton took Donald Trump to the house Monday night without even playing some of the heaviest cards against him”—notably the allegations against Trump University, the Trump Foundation, and Trump Model Management. Trump, meanwhile, didn’t criticize Clinton over the invasion of Libya and the subsequent attack on the U.S. compound in Benghazi, which happened under her watch as secretary of state.

But a different card that Trump didn’t play until after the debate suggests that he will only get nastier as the November election approaches. Speaking to CNN’s Dana Bash in the spin room on Monday night, Trump said, “I’m really happy I was able to hold back on the indiscretions in regard to Bill Clinton.” There’s every reason to believe that this is a not-so-veiled threat—that in claiming he showed heroic restraint in not smearing Hillary Clinton with her husband’s infidelity, he is in fact promising to do exactly that.

Recent history suggests he will. Trump reserved his most humiliating attacks for the tail end of the Republican primary, when such attacks appeared unnecessary because he was the prohibitive frontrunner. On the morning of May 3, he accused Ted Cruz’s father, Rafael, of being connected with the Kennedy assassination. Cruz’s campaign was already on its last legs, and would withdraw from the race that very night. On March 12, just three days before Marco Rubio would lose in Florida and withdraw from the presidential race, Trump tweeted:

Trump had been making fun of “Little Marco” for some time, but the accusation of corruption was a new one, and made at a moment when Rubio’s doom seemed certain.

Like Alec Baldwin’s character in 1992’s Glengarry Glenn Ross, Trump’s motto seems to be “always be closing.” And he’ll do anything to seal the deal. If he goes ugly even when he’s assured of victory, imagine what he’ll do if Clinton holds on to her lead and he’s faced with the prospect of defeat. Everything we know about his past and temperament suggests he’ll go ballistic on Clinton—and he’ll have plenty of enablers to provide him with ammunition.

If Trump were to wage all-out war on the Clintons, he could rely on a veritable ocean of muck that the American right wing has accumulated over the years, including not just Benghazi or the email scandal, but accusations going back decades about Whitewater, the suicide of Vince Foster, and drug smuggling in Arkansasnot to mention the likeliest line of attack: Bill Clinton’s checkered sexual history.

Roger Stone, a former Trump aide who’s still an ally, compiled a tome full of lurid stories in his 2015 book The Clintons’ War on Women, which has helped shape an increasingly powerful narrative on the right: that Bill Clinton is a sexual predator whose crimes also implicate his wife, for allegedly enabling him and for attacking his accusers. Nor is Stone merely crafting narratives. On the Alex Jones Show in May, Stone said he had set up a fundraiser to help Kathleen Willey, who has accused Bill Clinton of rape; Stone noted that Trump himself had contributed to the fundraiser.

The meme that Stone has honed has now become a standard Republican talking point. Congresswoman Marsha Blackburn, a Trump surrogate, told MSNBC on Wednesday, “Look at what she has done: Gennifer Flowers, Paula Jones, Monica Lewinsky, my goodness.” The same day, also on MSNBC, Trump surrogate Chris Collins said that “the women that Bill Clinton was involved with saw the wrath of Hillary Clinton.”

The element of truth to these accusations are that Bill was a serial philanderer and Hillary did, on occasion, respond to reports of his infidelity by trying to discredit the women who spoke about their relationships with him. Yet the Trump team takes this basic narrative and pushes it in slanderous directions the evidence doesn’t bear. On Monday night, after the debate, Rudy Giuliani said, “And after being married to Bill Clinton for 20 years, if you didn’t know the moment Monica Lewinsky said that Bill Clinton violated her that she was telling the truth, then you’re too stupid to be president.” Leave aside the hypocrisy of Giuliani, whose three marriages have been far from ideal, making this critique. What is striking is the word “violated.” By Lewinsky’s own testimony, it was a consensual affair between two adults.

While conspiracy theories about the Clintons have been around decades, Trump is in a unique position to mainstream the worst of these theories. As the Republican nominee, he has an entire party that, despite dissension, largely goes along with what he says. Any accusation he makes will have to be covered by the mainstream press and is likely to be echoed by the right-wing media and by many Republican politicians.

If Trump does decide to close ugly, he’ll have many allies to help him. So far, Hillary Clinton has been effective in turning Trump’s misogyny against him, putting him on the defensive for his countless sexist remarks, which have be a staple of Clinton ads. The question now is whether she can be equally effective at taking the sexist remarks about her, as Bill Clinton’s wife, and using them against Trump in a similarly devastating fashion.