Throughout the 2020 Democratic presidential primary, President Donald Trump didn’t have all that much to say about Sen. Kamala Harris (D-CA). In public and behind closed doors, the president preferred picking on several of Harris’ top competitors. But there was an aspect of her campaign that caught Trump’s attention and has stayed on his mind all this time: her support for having him criminally prosecuted once he’s no longer in power.

According to two individuals who spoke to the president earlier this summer about Harris, Trump made a point of trashing the senator for saying last year that based on the Mueller Report findings, under the next Democratic administration the Department of Justice would have “no choice” but to pursue obstruction of justice charges against Trump. “I’ve seen prosecution of cases based on much less evidence,” Harris, who was announced this week as presumptive 2020 Democratic presidential nominee Joe Biden’s VP pick, told NPR.

One of the sources said the president recently mocked Harris for making a big deal about the DOJ potentially prosecuting him after he leaves office, saying she wanted to play “tough.” Trump, this source recounted, said he thought she was just “bluffing” and that she and other Democrats are just craving another “witch hunt.” In the same conversation, the president also made fun of Harris’ call at a Democratic debate late last year to have Trump kicked off Twitter.

“Criminal prosecution of President Trump? [Kamala] must be smoking something,” John Dowd, a lawyer who represented Trump for nearly a year of Special Counsel Robert Mueller’s Russia probe, said in a brief interview on Thursday. “The American people are very smart. They figure these things out pretty easily. There’s not going to be any prosecution of the president after he leaves office.”

A third source who spoke to the president about the senator in the past year said Trump had jokingly accused Harris of “ripping him off” by “swapping in ‘Lock Him Up’ in place of ‘Lock Her Up,’” Trump’s longtime anti-Hillary Clinton rallying cry.

“Maybe some of these people that vote in Democratic primaries, they want Donald Trump prosecuted when he leaves office. Maybe [Harris is] just appealing to them?” Fox News host and Trump pal Jesse Watters said during a June 2019 segment. “She went even farther [than calling for impeachment] and said [she] wants him behind bars after he leaves office. That’s a big difference.”

Nowadays, the liberal lawmaker is taking up a lot more of Trump and his political operation’s time. The president calls Biden’s newly named running mate “nasty” and insists that she is somehow more left-wing than her former 2020 competitor Bernie Sanders, the self-proclaimed socialist senator. His 2020 campaign staff are determined to paint her as a radical, “phony,” power-hungry operator who’s guilty of being both too tough on crime and also too soft on crime. And some of Trump’s top associates and media allies are resorting to increasingly dirty smears.

The president, for one, has already started dabbling in baseless birtherism allegations against Biden’s running mate, just as he did for so long against former President Barack Obama.

But to Trump’s current and former attorneys, Harris’ insistence that the president should face prosecution after he leaves the White House remains an unforgivable, or laughable, offense—one that might even foreshadow legal jeopardy for Trump when someone else occupies the Oval Office.

Of course, Trump himself has for years made the criminal prosecution of his political nemeses and “deep state” actors a hallmark of his rhetoric and his own demands of his DOJ.

Jenna Ellis, a senior legal adviser to Trump and his campaign who described the legality of Harris’ run as an “open question,” told The Daily Beast: “Harris’ record [as a longtime prosecutor] is that she is a malicious prosecutor. Statements like that are fully in line with her terrible record of using her position for political prosecutions. Democrats don’t care about law and order, they only care about abusing their own political power.”

On Thursday evening, Rudy Giuliani, who in his time as Trump’s personal lawyer played a central role in the Ukraine saga that triggered his client’s impeachment, simply said Harris “was an entirely unprincipled prosecutor. She was a bully. She mounted up convictions against little people for little crimes and ran away from all tough and political cases.”

If Team Biden is victorious come November, it would be wildly improper for a President Biden and a Vice President Harris to order or pressure the Justice Department to charge their former top political rival, and Biden has said as much. In an interview this month with members of the National Association of Black Journalists and National Association of Hispanic Journalists, Biden stressed, “I will not interfere with the Justice Department’s judgment of whether or not they think they should pursue a prosecution.”

The Obama VP promised that “in terms of saying, ‘I think the president violated the law. I think the president did this, therefore, go on and prosecute him’—I will not do that.” 

Biden added, however, “If [a case] prove[s] to be a criminal offense, then in fact, that would be up to the attorney general to decide whether he or she wanted to proceed with it. I am not going to make that individual judgment.”