An up-and-coming progressive blogger was purportedly fired Friday for his Twitter fight with one of the movement’s most power figures, Neera Tanden, president of the Center for American Progress.

The exchange started when Matt Bruenig, a blogger for the liberal think tank Demo, started tweeting about an unflattering story in The Nation about Bernie Sanders supporters, according to Gawker.

Tanden was a policy adviser for Presidents Bill Clinton and Barak Obama and for Hillary Clinton’s 2008 White House bid.

The Center for American Progress is a research group whose public policy work has for decades shaped the political agenda of progressives and other elected Democrats.

The group’s first president was John Podesta, Hillary Clinton’s 2016 campaign director and a Bill Clinton chief of staff.

Tanden eventually entered the Twitter exchange Friday between Bruenig and the author of The Nation story, tweeting: “Good to know this stuff isn't just for me!”

Bruenig responded with several caustic tweets including one about Taden’s alleged endorsement of cutting welfare benefits for the poor.

“You don’t get to be president of CAP without starving some poor mothers,” he wrote in one tweet.

In subsequent tweets, Bruenig called Tanden “geriatric” and wrote: “[Expletive] Neera uses welfare when she needs it then takes away from others when they need it. Disgusting.”

Tanden has purportedly acknowledged her family having needed welfare. She apparently has never backed welfare reform. But Tanden was a policy adviser in the Clinton administration that reduced welfare benefits in 1996.

Demo told Gawker that the group and Bruenig were “parting ways,” after having “agreed to disagree on the value of the attack mode on Twitter.”

Gawker reports that a source said Bruenig was fired.

Demo made an online apology for Bruenig’s offensive remarks and suggested in a press release that his employment was terminated upon learning the extent of his “online harassment of people with whom he disagrees.”

Bruenig has declined to comment.

Tanden purportedly told Gawker in an email: “I find the whole situation unfortunate. Mr. Bruenig has made contributions on the poverty discourse and I wish him well in the future. I would welcome an actual discussion of ideas with him.”