Topeka ? A state senator switched parties Thursday, four months after Gov. Kathleen Sebelius and a legislative leader helped engineer his defeat in this year’s Democratic primary.

Sen. Mark Gilstrap, of Kansas City, said he is breaking his family’s 160-year-old ties to the Democratic Party because it developed a “radical liberal tilt and intolerance of dissent.” Gilstrap broke with Sebelius over issues such as energy and abortion before the election.

“There used to be such a thing as conservative Democrats in Kansas. But they are rapidly becoming extinct,” Gilstrap said. “The party has shifted radically to the left, and Kathleen Sebelius has led that shift.”

Gilstrap gives up his seat representing the 5th District on Jan. 12, when his current, four-year term expires. He’ll be replaced by Kelly Kultala, also from Kansas City, who defeated him in the primary.

Both Sebelius and Senate Minority Leader Anthony Hensley, a Topeka Democrat, endorsed Kultala and helped raise money for her during the primary.

In one letter, Sebelius described Kultala as “a real Democrat.” Hensley once derided Gilstrap in an e-mail as “a Democrat in name only” and accused Gilstrap of supporting “a right-wing agenda” in line with conservative Republicans.

Sebelius declined to comment Thursday about Gilstrap’s decision.

But Larry Gates, the Kansas Democratic Party’s chairman, said: “It’s clear Mark has found an organization more representative of his own ideologies, just as the voters in the 5th District have now elected the senator who best represents theirs.”

Gilstrap first won his Senate seat in 1996, then was re-elected in 2000 and 2004. This year, Gilstrap broke with Sebelius over two proposed coal-fired power plants in southwest Kansas.

Gilstrap already had upset some fellow Democrats in 2006 by endorsing Republican Attorney General Phill Kline’s unsuccessful bid for re-election.