HARRISBURG, Pa. — A Democrat in Pennsylvania’s state Senate from an area that shifted decisively to support Donald Trump in 2016’s presidential election is switching his registration to become an independent and will caucus with the Republican majority.

Sen. John Yudichak of Luzerne County said in a statement Tuesday that registering as an independent is the only way he can “faithfully and fully” serve the people of his northeastern Pennsylvania district.

He also criticized the politics of “extremist” ideologies.

“I choose the politics of ‘we’ over the politics of ‘us versus them,’” Yudichak said. “I choose to reject the ‘purist’ politicians who now stand as unyielding impediments to the only thing that motivates me to be in politics — getting real things done that make a true difference in people’s lives.”

Viewed as a moderate, Yudichak, 49, has occasionally split with Democratic leadership on floor votes. He was the party’s longtime chair of the Environmental Resources and Energy Committee, and coming from a historic coal region often put him at odds with environmental advocacy groups that favor renewable energies.

Yudichak, who endorsed Democrat Joe Biden for president last month, has also had his eye on higher office, telling colleagues recently that he was considering running for state auditor general.

His seat seems safe: he didn’t even have an opponent in the primary or general election last year on his way to winning a third term.

Republicans hold 27 seats in the 50-seat chamber, with one solidly Republican district temporarily vacant until the winner of a Jan. 14 special election is sworn in. Counting Yudichak and the vacant seat, Republicans will likely have an effective 29-21 majority next year.

In a statement, Senate Minority Leader Jay Costa, D-Allegheny, said Democrats were “extremely disappointed” to see Yudichak turn his back on their “large tent” values.

Yudichak’s departure comes after Democrats picked up six seats in the past year, substantially changing the profile of the caucus to become more liberal and shifting its powerbase to southeastern Pennsylvania. It also comes as Democrats had eyed the potential in 2020 of capturing the Senate majority for the first time in nearly 30 years.

Yudichak’s home county, which had long supported Democrats, flipped unexpectedly in 2016 to support Trump over Democrat Hillary Clinton, although Democratic Gov. Tom Wolf won Luzerne County in last year’s election.

His Senate district has a heavy Democratic registration advantage, although it is whiter, with lower median incomes and lower rates of college-degree attainment than the rest of Pennsylvania.

Before getting elected to the Senate in 2010, Yudichak served 12 years in the state House of Representatives.