Marquette, Mich. ? Rep. Bart Stupak insists that tea party activists outraged over his crucial support of health care legislation didn’t run him out of office, but his decision to retire gives conservatives a rallying point as they target Democrats in the midterm elections.

The congressman, an anti-abortion Democrat whose high-profile role in the “Obamacare” debate earned him enemies on the left and the right, said Friday that he’s leaving because he’s tired and has accomplished his No. 1 goal: improving health care.

“The tea party did not run me out,” Stupak told The Associated Press in a phone interview. “If you know me and my personality, I would welcome the challenge.”

Stupak had been a consistent landslide winner in his sprawling northern Michigan district, and the opening now offers Republicans a ripe opportunity to regain a seat they held for decades until Stupak prevailed in 1992.

His political foes — tea party activists and abortion opponents — both claimed credit for forcing him into retirement, and Michigan GOP Chairman Ron Weiser declared that the nine-term incumbent had become the first casualty of the battle over health care in Congress.

“Bart Stupak’s decision to retire is emblematic of the many Democrats in swing districts who have been forced into casting tough votes in favor politically unpopular policies at the behest of House Speaker Nancy Pelosi,” added Ken Spain, communications director for the House Republican campaign committee.

No prominent or well-funded Republican, however, had stepped in to challenge Stupak, who said he was confident of winning re-election. The 58-year-old said he was withdrawing because he was worn out and wanted more family time after nearly 18 years in Congress and the grueling health care battle.