The Tea Party Express credited its influence on Friday in "defeating" Michigan Rep. Bart Stupak--a key target of the conservative activists who barreled into his district a day earlier to rally against him.

"The surprising announcement that Congressman Bart Stupak is abandoning his campaign for reelection shows the power of the tea party movement," the group's political director, Bryan Shroyer, said in a statement.

"Stupak was no longer able to hide his betrayal of conservative principles because the tea party movement was determined to educate the voters in the district," he said.

Stupak, a pro-life Democrat representing Michigan's 1st congressional district, was under attack by the tea party movement and other conservative groups for his vote in favor of the Democratic health care legislation.

"I absolutely credit the mere threat of us coming through his district," Tea Party Express chairman Mark Williams told FoxNews.com. "We put the nail in the coffin."

The Tea Party Express, one of the most visible factions of the movement, rolled into Bessemer, Mich., late Thursday to stage a rally targeting Stupak. The group also launched an aggressive ad campaign against him – with the group’s political action committee, Our Country Deserves Better, pledging $250,000 in radio and T.V. ads aimed at ousting him from office.

The group had planned 11 rallies in the state over the next three days, protesting Stupak's controversial vote and calling for his swift resignation.

Williams said Stupak's announcement on Friday in no way disrupts their plans.

"Now it becomes a celebration of the process and the power of the people," he said.