On Monday, Messing, 50, tweeted, "Hey Susan Sarandon, how are you liking the revolution?"
She didn't tag Sarandon, 72, in her tweet, but the "Thelma & Louise" star still spotted the dig.
Sarandon replied with a photo advertising BernieSanders.com and wrote, "Happy so many ideas labeled impossible/radical in 2016 like Medicare 4 All, fighting climate change, $15 min wage & tuition free college are now mainstream & supported by majority. Racial, economic & social injustice must be addressed with systemic change. You’re welcome to join."
Sanders' supporters and Sarandon fans were quick to blast Messing, including resurfacing a 2017 tweet in which she complained about higher taxes for the wealthy.
The "Will & Grace" actress has attacked Sarandon repeatedly for not voting for Hillary Clinton in 2016.
In September 2018, Messing slammed “Thelma & Louise” actress Susan Sarandon in a series of tweets, telling her to “shut the f--- up” after Sarandon told Variety in an interview that Trump has “if anything, inspired more women and people of color to run for office.”
"STFU SUSAN," Messing tweeted. "Oh yes, PLEASE let’s give Trump CREDIT. I mean how else are you able to walk out on the street."
Sarandon responded, “Debs, before you get yourself all self-righteous try clicking on the video and listening to what I actually say, not @Variety's clickbait headline, which btw has no quotation marks. That’s a clue..."
In a two-minute video, Variety's interviewer asked Sarandon what “grade” she would give President Trump, to which the actress replied: "I'd tell him to start all over again." Without giving Trump a grade, Sarandon went on to give an overview of the political landscape.
During her explanation, Sarandon briefly mentioned how more women and people of color are running for office, but did not seem to directly credit Trump.
In October 2018, Messing admitted she'd rather share an elevator with Trump than with Sarandon.
According to People, Messing and Sarandon first got into it in 2016 after Sarandon seemed to suggest she would vote for Trump over Clinton during an appearance on MSNBC’s "All In With Chris Hayes."
Fox News' Sasha Savitsky contributed to this report.