The former Richard Nixon and Ronald Reagan aide on Thursday launched a new super PAC aimed at taking down the Florida senator in the GOP presidential primary and boosting the billionaire mogul.
Stone announced his new effort in an email asking for donations from "average Americans" on Thursday that was sent to conservative Newsmax readers and shared with CNN.
The letter signed by Stone was a point-by-point indictment of Rubio and argument in favor of Trump.
"It is vital that voters know about the real Marco Rubio, his liberal voting record and limited experience," Stone wrote. "Marco Rubio intends to present himself to the voters of New Hampshire, Iowa, South Carolina, as another Ronald Reagan. In fact, he is a wheeler-dealer who has played ball with the Obama administration on numerous issues such as immigration and trade. That's why we've formed the Committee to Restore America's Greatness."
The letter says Rubio has been anointed by a Republican establishment, dubbed "losers," that produced the failed campaigns of Mitt Romney and John McCain. Stone also writes that candidate was originally supposed to be former Florida Gov. Jeb Bush, and that Bush has fallen to fifth place in the face of Trump's "low energy" attacks.
It also accuses Rubio of entering a "secret alliance" with Ohio Gov. John Kasich to attack Trump. A Kasich-supporting super PAC has released some of the most aggressive attack ads going after the front-runner. New Jersey Gov. Chris Christie also gets a brief mention in a postscript at the end of the letter, including a mention of his office's "Bridgegate" scandal.
The letter is a litany of Rubio's alleged anti-Republican indiscretions, including supporting the "Gang of Eight" immigration bill and supporting the Trans-Pacific Partnership.
Stone also uses colorful language to portray Rubio being in billionaires' pockets.
"I must question whether Marco Rubio has the experience, intellectual heft, or principles to be president of the United States. Would Rubio simply be a shill for the billionaires?" he wrote. "Make no mistake, Rubio's New America is the wet dream of the crooked lobbyists, Wall Street billionaires and special interests."
Trump, a billionaire in his own right, has pledged repeatedly throughout his campaign to self-fund and not accept super PACs' money. He decries politicians being owned by wealthy donors.
Stone's PAC insists it will not accept money from corporations, asking "average Americans and everyday citizens to help us finance a hard-hitting television and radio campaign exposing the real Marco Rubio, and his secret deal with would-be vice president John Kasich."
Stone declined to comment to CNN beyond the letter.
Stone parted with Trump's campaign in August amid controversy over whether he quit or was fired. He insisted he left on his own terms.
The committee filed for recognition with the Federal Election Commission in October.