The Massachusetts Republican party gathers Saturday for its nominating convention — but one leading candidate for congress won’t be there.

Richard Tisei, the GOP’s candidate for lieutenant governor four years ago, will boycott the convention because of the socially conservative platform the party adopted.

"I feel as though if I go, I’m giving tacit approval to that platform, and don’t feel comfortable being there," Tisei said.

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The Republican State Committee last month approved a platform that supports "traditional marriage" and calls every instance of abortion tragic.

Tisei is gay and married and supports abortion rights.

He is challenging Democratic U.S. Rep. John Tierney to a rematch in the Sixth District.

Tisei’s former running mate, Charlie Baker, will attend the convention. Baker is running for governor on the Republican side. While he is also pro-choice and pro-same sex marriage, Baker needs to be nominated by delegates at the convention while Tisei does not.