The group is run by a number of former Clinton staffers and supporters, but Carville is the closest person to Clinton's inner circle who's publicly jumped on board with the effort. He ran Bill ClintonWilliam (Bill) Jefferson ClintonMueller’s probe doesn't end with a bang, but with a whimper Mark Mellman: History’s judgment Congress should massively ramp up funding for the NIH MORE's 1992 campaign, was an adviser and top media surrogate for Hillary in 2008, and remains close friends with the Clintons.

The Hill has confirmed Carville's involvement with the group. The Hill first reported the group's formation.

"There hasn't been a presidential election in my lifetime when Democrats have been as united behind a potential candidate as we are today. The enthusiasm and hunger for a Hillary ClintonHillary Diane Rodham ClintonGrassley blasts Democrats over unwillingness to probe Clinton GOP lawmakers cite new allegations of political bias in FBI Top intel Dem: Trump Jr. refused to answer questions about Trump Tower discussions with father MORE Presidency is unlike anything I've ever seen. So I'm not going to waste my time writing you about how great Hillary is or how formidable she’d be – you know it all already," Carville writes in an email to the group. "But it isn't worth squat to have the fastest car at the racetrack if there ain't any gas in the tank — and that's why the work that Ready for Hillary PAC is doing is absolutely critical. We need to convert the hunger that's out there for Hillary's candidacy into a real grassroots organization."

Carville has previously made it clear he wants Hillary to run: he's said the pressure from Democrats for her to run will be "unimaginable," and predicted she'd clear the primary field.

This post was updated at 12:20 p.m.