West Virginia Democratic primary voters opted not to nominate Rep. Alan Mollohan for a 15th term.
Mollohan's loss is the first defeat for a House incumbent this cycle and comes days after Sen. Bob Bennett (R-Utah) was denied his party's nomination for a fourth term at the GOP state party convention in Salt Lake City.
In West Virginia, Democrats nominated state Sen. Mike Oliverio, who claimed 56 percent of the vote to Mollohan's 44 percent with 511 of 670 precincts reporting. The Associated Press called the race for Oliverio.
Mollohan's vote for healthcare reform had angered some of his constituents and had turned national anti-abortion groups against him.
"Just as Bart Stupak did, Congressman Mollohan now fully realizes that votes do have consequences," Marjorie Dannenfelser, head of the Susan B. Anthony List, said in statement. "Mollohan's loss comes as a direct result of his vote for healthcare reform that included federal funding of abortion."
Oliverio, who has spent two decades in the state Legislature, targeted Mollohan on ethics in his TV advertising. That appearance of corruption, in the context of the current national environment, tilted the race his way, sources said.
Mollohan was investigated by the Justice Department last year for the rapid expansion of his personal wealth. No charges were filed.
Oliverio also attacked Mollohan, a senior member of the Appropriations Committee, for his earmarks.
Democratic Congressional Campaign Committee chairman Rep. Chris Van Hollen (D-Md.) thanked Mollohan for his service and expressed confidence Democrats would hold the seat in November.
"This was a tough and spirited primary process and we are confident that this historically Democratic seat will remain Democratic this November," he said in a statement.
On the Republican side, former state GOP chairman David McKinley edged out businessman Mac Warner to claim the nod. The two dominated the vote in the six-person GOP field, with McKinley capturing 36 percent of the vote to Warner's 25.
Mollohan was first elected to Congress in 1982, winning the seat held by his father. He had not faced a serious primary challenger since 1998. Sen. John McCain (R-Ariz.) carried the district with 57 percent in 2008.
-- This post was updated at 10:21 p.m.