LANSING, Mich. -- U.S. Rep. Thaddeus McCotter of Michigan should have had an easy time knocking off a little-known opponent in the Republican primary and winning a sixth term this fall in his GOP-leaning district. Instead, he's fighting for his political life after saying Tuesday he'll be forced to run a write-in campaign because his staff didn't file enough valid petition signatures to get him on the Aug. 7 ballot.

McCotter ran a little-noticed GOP presidential campaign last year before asking voters to re-elect him to his Detroit-area congressional seat, prompting other prominent Republicans to stay out of the race. The lone Republican left on the ballot is Kerry Bentivolio, a 60-year-old Vietnam War veteran, teacher and beekeeper from Milford.

Write-in campaigns are expensive, because candidates have to educate voters on how to cast a write-in ballot. However, Alaska Sen. Lisa Murkowski ran a successful general election write-in campaign in 2010 after losing the GOP primary. Murkowski became the first person since 1954 to win a write-in campaign for U.S. Senate.

McCotter, who was first elected to Congress in 2002, made the stunning disclosure Friday that the Michigan secretary of state's office determined he didn't have the 1,000 valid signatures needed to get on the primary ballot, even though 2,000 signatures were turned in. McCotter released a statement Tuesday urging the secretary of state's and attorney general's offices to investigate the petitions to determine what happened.

Secretary of state spokesman Fred Woodhams said Tuesday that only 200 to 300 of the signatures appeared valid, with many appearing to be copies. If duplicate signatures from the same day are turned in, both sets are thrown out.

Woodhams said the secretary of state's office has turned over information on McCotter's petitions to the attorney general's office. A spokeswoman says officials are reviewing the information to determine if evidence of election law violations exists.

McCotter, who is running for re-election in Michigan's 11th Congressional District, also made comments blaming others for the faulty signatures, though he acknowledged it was up to him to "clean up" the situation.

"The buck stops with me," McCotter said in his statement. "That's why I urge the continued investigation into the petitions. Everyone deserves to know what happened regarding this filing."

Bentivolio has been endorsed by FedUpUSA, a nonprofit group that also backs Troy Mayor Janice Daniels, a tea-party favorite facing a recall effort in her Oakland County community. Bentivolio told The Associated Press on Saturday he was "excited about" how McCotter's miscue might help his congressional campaign.

Other Republicans considered getting into the race last year when it appeared McCotter, 46, might focus on his long-shot presidential bid rather than run for re-election. But they decided not to challenge the guitar-playing congressman from Livonia once he made it clear he was running.

Former state Rep. A. Rocky Raczkowski said Tuesday he might run his own write-in campaign, even though Raczkowski, a Republican, supported McCotter in the past.

Two Wayne County residents, William Roberts of Redford Township and Oakwood Hospital chief of medicine Taj Syed of Canton Township, have filed to run in the Democratic primary.

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