Republican challenger Tim Walberg upset Rep. Joe Schwarz in Tuesday's GOP primary in southern Michigan, using a staunchly conservative message and help from the Washington-based Club for Growth to defeat the first-term congressman.

With 73 percent of the precincts reporting, Walberg had 55 percent, or 26,295 votes. Schwarz had 45 percent, or 21,617 votes.

"I look at this election as probably a victory for Right to Life, anti-abortion, anti-embryonic stem cell groups but it's a net loss for the Republican party because it just pushes the party farther to the right," Schwarz said in an interview. He called Walberg to concede the race.

Schwarz, R-Battle Creek, had tried to fend off Walberg, R-Tipton, in a rematch of sorts in the 7th Congressional District. The first-term congressman defeated Walberg and four conservatives with only 28 percent of the vote in the 2004 GOP primary and was targeted this year by the conservative Club for Growth, which poured in advertising and fundraising dollars.

Walberg led Schwarz by wide margins in Lenawee County, his home, and Hillsdale County, a conservative region of the state. Schwarz led in Calhoun County and had a slight lead in Eaton County, areas he represented in the state Senate. Walberg led in Jackson County, the most populous in the district.