Republican Rep. Joe Schwarz is backed by President Bush, Arizona Sen. John McCain and the National Rifle Association.

In most years that would be more than enough to recapture the nomination in this rural Michigan district where the Republican Party blossomed.

But this year may be different.

Schwarz, a 68-year-old moderate Republican, was a fixture in local and state politics for 25 years before winning a seat in Congress in 2004. But in a primary that has topped $1 million in spending by outside groups and generated bad blood between the two candidates, Schwarz faces a serious challenge from conservative former state lawmaker Tim Walberg in Tuesday's primary.

The solidly Republican district includes Jackson, where the Republican Party had its first official meeting in 1854. In the district a struggle over GOP principles is being played out at a time when Republicans acknowledge that their hold on Congress is at stake this fall.

The winner will be heavily favored in November, but some party strategists wonder if the influx of television and radio ads, mailers and spats over abortion, taxes and the budget would be better off directed elsewhere.

"Under normal circumstances, primaries strengthen the party," said Scott Reed, who managed Bob Dole's 1996 presidential campaign. "But in this case, it feels like we're spending a lot of resources that we should be saving for November."

Republicans are also pitted against each other in Rhode Island, where Sen. Lincoln Chafee faces a conservative challenger in September's primary. In Connecticut, Democrats will vote Tuesday in a primary between hawkish Sen. Joe Lieberman and anti-war candidate Ned Lamont.

Schwarz's seat has been put in the crosshairs by the conservative Club for Growth, which has spent more than $400,000 in independent expenditures while directing donors to support Walberg, who has received most of his $600,000 in funding from outside the district.

Club for Growth President Pat Toomey, a former Pennsylvania congressman who narrowly lost a primary against Sen. Arlen Specter in 2004, rejects the notion that primary fights hurt Republicans.

"The more races in which we're able to help good, pro-growth, limited government candidates win, the better the chances Republicans have of holding the House, which I think is a dicey proposition right now," Toomey said. "We're the voice out there saying 'Hey guys, the Republican Party's got to stand for something."'

Schwarz has received help from the moderate Republican Main Street Partnership. Executive Director Sarah Chamberlain said her organization expects to spend $600,000 on the race, "which could have been better spent against Democrats in the fall."

"To me, control of the House is clearly at stake and this is a million dollars that could be better spent helping the bottom line," said Rep. Fred Upton, R-Mich., a Main Street member.

Schwarz, a physician from Battle Creek, won the Republican primary in 2004 with 28 percent of the vote when Walberg and five other conservatives split the vote. Private polls have shown a close race after Walberg branded Schwarz as too liberal on abortion, taxes and immigration.

"I am a conservative. I believe in limiting government through reducing taxes and cutting spending ... and speaking for strong support of traditional values," Walberg said Saturday.

Schwarz contends Walberg has badly twisted his record and accused the Club for Growth of hijacking the primary. Both campaigns have filed complaints with the Federal Election Commission while the tone has grown increasingly negative.

"They're trying to buy the seat," Schwarz said. "That to me is the worst of politics."