Progressive billionaire George Soros says former President Barack Obama is his “greatest disappointment.”

George Soros, an early backer of Barack Obama’s 2008 presidential run, described the former president as “his greatest disappointment,” in an interview with The New York Times published on Tuesday. On the advice of an aide to Soros present during the interview, the open-borders financier made clear his disappointment came on a “professional level.”

According to Soros, the Democrat lawmaker “closed the door” on him after winning the White House. “He made one phone call thanking me for my support, which was meant to last for five minutes, and I engaged him, and he had to spend another three minutes with me, so I dragged it out to eight minutes,” the progressive billionaire recounted to the paper, later adding Obama had a reputation of taking “his supporters for granted.”

Neera Tanden, head of the left-leaning group Center for American Progress, revealed in a May 2012 email to Hillary Clinton that Soros admitted to her that he regretted supporting Barack Obama’s 2008 presidential campaign.

“I told him I worked for you in the primaries and he said he’s been impressed that he can always call/meet with you on an issue of policy and said he hasn’t met with the President ever (though I thought he had),” wrote Tanden. “He then said he regretted his decision in the primary – he likes to admit mistakes when he makes them and that was one of them.”

Soros and Obama eventually got together in New York City after a failed attempt to schedule a White House meeting. Obama’s handlers “pissed on him,” a source close to the progressive billionaire told the New Yorker. “He didn’t want a fucking thing! He didn’t want a state dinner, or a White House party—he just wanted to be taken seriously.”

Despite their frosty relationship, organizations supported by the two men are working together to oppose President Donald Trump’s agenda. Organizing for Action, an off-shoot of Barack Obama’s first presidential campaign, partnered with the Soros-backed Indivisible Project for “online trainings” on how to build protest movements in the Trump-era.

“Dubbed ‘Indivisible,’ the group launched as a way for Padilla and a handful of fellow ex-Democratic aides to channel their post-election heartbreak into a manual for quashing President Donald Trump’s agenda. They drafted a 26-page protest guide for activists, full of pointers on how to bird dog their members of Congress in the language of Capitol insiders,” Politico reports.

“Even the safest [Republican] will be deeply alarmed by signs of organized opposition,” says the manual, “because these actions create the impression that they’re not connected to their district and not listening to their constituents.”

Protesters are encouraged to film Republican candidates in hopes they can be portrayed in a negative light. “Unfavorable exchanges caught on video can be devastating” for GOP members when “shared through social media and picked up by local and national media.”