PROVIDENCE, R.I. (WPRI) – A decade after they were rival candidates for U.S. Senate, Lincoln Chafee is backing Matt Brown in his Democratic primary challenge against incumbent Gov. Gina Raimondo.

Chafee, who became a Democrat five years ago, made the endorsement Thursday in a news release issued by the Brown campaign. Chafee himself had considered a primary bid against Raimondo this year, then briefly flirted with a challenge to U.S. Sen. Sheldon WhItehouse before declining to run.

“I support Matt because he’s in it for the right reasons and always has been,” Chafee said in a statement. He described Brown as “a proven, hard-working, intelligent public servant” and said he “will restore competency to the running of state government.”

Chafee is the most high-profile Rhode Island politician to back Brown, who is trying to tap into energy among progressive Democrats as the Sept. 12 primary approaches.

Chafee’s dislike for his successor is deep and longstanding. He and Raimondo have disagreed on a number of issues, and they’ve also clashed personally. (A deposition revealed that during his time as governor, Chafee was pocket-dialed by a staffer who was getting drinks with Raimondo – leaving him a voicemail of their conversation criticizing him.)

“Governor Raimondo’s idea of economic development is doling out huge taxpayer giveaways to handpicked corporations that donate to her campaign, while underfunding programs and services on which hundreds of thousands of Rhode Islanders depend,” Chafee charged. “Studies have shown that this form of corporate welfare is a strategy that is ‘shortsighted,’ ‘senseless and foolhardy.'”

Raimondo’s spokeswoman, Emily Samsel, shot back: “Brown and Chafee have a lot in common. Neither man has accomplished much to help everyday Rhode Islanders keep up and get ahead. Both have history of hopping in and out of the Democratic Party when it’s politically expedient.” (Brown began his campaign for governor as an independent, before switching to the primary.)

“Governor Raimondo has been tirelessly fighting for people being left behind in today’s America, no thanks to Matt Brown, who disappeared from Rhode Island after his last campaign collapsed and was nowhere to be found as so many people pitched in to make a difference in our state,” Samsel said. She highlighted the governor’s support for gun control, abortion rights and “Dreamers,” as well as her opposition to President Trump’s policies.

Brown and Chafee have a history, too: in 2006, when Chafee was still a Republican U.S. senator and Brown was a Democratic secretary of state, Brown made an aborted bid for the Democratic Senate nomination against Chafee that eventually went to Whitehouse.

Chafee was elected governor as an independent in 2010, four years after he lost his U.S. Senate seat. He became a Democrat in 2013, but declined to seek re-election amid low poll ratings. He backed Clay Pall over Raimondo and Angel Taveras in the 2014 Democratic gubernatorial primary. (Pell and Taveras are backing Raimondo this year.)

Ted Nesi (tnesi@wpri.com) covers politics and the economy for WPRI.com. He is a weekly panelist on Newsmakers and hosts Executive Suite. Follow him on Twitter and Facebook