Beth Myers and Peter Flaherty, two longtime members of Mitt Romney’s inner circle, have signed on to help Republican Senate candidate Michael J. Sullivan, adding to a split among Romney loyalists in the three-way race.

Flaherty was deputy chief of staff during Romney’s governorship, and a top adviser on both his presidential campaigns, with a special focus on helping to woo evangelical Christians and social conservatives who were wary of Romney’s Mormon faith. Flaherty also advised Scott Brown’s Senate campaigns.

Myers was Romney’s chief of staff during all four years of his governorship, and then served as campaign manager for his 2008 presidential bid and senior adviser to his presidential campaign in 2012.

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She recently made news by joining a list of prominent Republicans who are urging the Supreme Court to declare that same-sex couples have a constitutional right to marry.

“It seems every day our team is growing and the addition of Beth and Peter just demonstrates how committed we are to winning this race and improving this economy for the people of Massachusetts and across the country,” Sullivan said in a statement. “I am thrilled to have Beth and Peter join us and look forward to their advice and guidance.”

While Flaherty and Romney are backing Sullivan, Romney’s onetime aides are not united in their support of his candidacy.

Kerry Healey, who was Romney’s lieutenant governor, Bradley D. Crate, who was chief financial officer for Romney’s 2012 presidential campaign, Gail Gitcho, who was a Romney spokeswoman, and Will Ritter, a former Romney campaign aide, have all signed on with the Senate campaign of Gabriel E. Gomez, a private equity investor and onetime Navy SEAL.

The third candidate in the race, state Representative Daniel B. Winslow, served as chief legal counsel for part of Romney’s governorship. Charles Pearce, who was trip director for Romney’s 2012 presidential campaign, is now working for Winslow as a spokesman.