This is not the first time that the idea of a presidential self-pardon has come up. Last July, The Washington Post reported that Trump had asked about his ability to grant pardons to himself or family members. Then-White House Communications Director Anthony Scaramucci and Trump lawyer Jay Sekulow both insisted the report was untrue, though the president hedged in a tweet: “While all agree the U. S. President has the complete power to pardon, why think of that when only crime so far is LEAKS against us.FAKE NEWS.”

The president’s assertion comes after a series of pardons that are atypical in timing and in recipient. They have overwhelmingly gone to conservative political celebrities: former Sheriff Joe Arpaio, convicted of contempt of court; former Dick Cheney aide Scooter Libby, convicted of perjury; and, most recently, pundit Dinesh D’Souza, convicted of campaign-finance fraud. (Trump also pardoned a sailor convicted of illegally taking photos on a submarine and the late boxer Jack Johnson, and has floated a pardon and commutation for Martha Stewart and former Illinois Governor Rod Blagojevich, respectively, both of whom are Democrats and were involved in The Apprentice.)

These moves have led critics to worry that Trump is either telegraphing to friends caught up in the Russia investigation that he will pardon them; laying the groundwork to normalize plainly political pardons, including perhaps his own; or both.

The thing about Trump’s pardons for Arpaio and D’Souza in particular—as well as any hypothetical pardon for himself—is that they are at once outrageous and at the same time likely legal. The presidential pardon power is extremely broad and is enumerated in the Constitution. No president has ever tried to pardon himself, so it’s an untested proposition whether courts would allow it, though some legal scholars believe it’s possible.

Yet a self-pardon would be, ironically, self-incriminating, indicating that the president at the very least believed he was likely to be charged with a crime, even if he didn’t believe he committed one. Moreover, it would make it much easier for a president to commit crimes with less fear of repercussions. The only recourse would be removal by Congress.

For this reason, Trump lawyer Rudy Giuliani has argued that the president would not pardon himself. “The president of the United States pardoning himself would just be unthinkable,” he told NBC’s Chuck Todd on Sunday. “And it would lead to probably an immediate impeachment. You know you get your House, Senate would be under tremendous pressure.” Chris Christie, the former governor of New Jersey and a Trump confidant-turned-occasional critic, said the same.

Nonetheless, the way that Trump and his allies are speaking about a self-pardon, and linking it to impeachment, looks a lot like a trial balloon. Republicans, as well as many Democratic leaders, believe that talk of impeachment will only help Trump and the GOP, so Giuliani may have ulterior motives for injecting it into the conversation. Moreover, speaking publicly about the president pardoning himself helps make it a topic of conversation and therefore potentially more acceptable. Even if it seems unthinkable and impeachment-inducing now, the story of Trump’s political career is repeatedly making the unthinkable not only thinkable, but real.