(Image Credit: Tom Williams/Getty Images)

Rep. Thaddeus McCotter has had a rough year.

The Michigan congressman's long-shot GOP presidential bid never gained steam, fizzling out three months after it formed. His U.S. House re-election prospects hit a major stumbling block last week after he failed to qualify for the primary ballot. He is being investigated for fraud after allegedly submitting fake signatures on his election petitions.

And now, amid the investigation, McCotter says he will give up his seat in the House of Representatives at the end of this term, ending his write-in, re-election campaign.

"One can't clean up a mess multitasking," the five-term congressman wrote in a statement Saturday. "Honoring my promise to the sovereign people of our community only allows me to finish the official duties of my present congressional term; and aid the State Attorney General criminal investigation that I requested into identifying the person or persons who concocted the fraudulent petitions that have cost me so dearly."

It's unclear whether the guitar-playing congressman will keep his spot in the House band, The Second Amendments, where he plays lead guitar with three other congressmen.

The Michigan Secretary of State's office announced last week that of the 1,833 signatures McCotter's campaign submitted to qualify for the GOP primary ballot, only 244 were valid. Hundreds of the signatures were apparently photocopied, digitally altered and re-pasted multiple times onto blank petition forms, said Fred Woodhams, a spokesman for the Michigan State Department.

While it is extremely rare for a congressional incumbent to fail to meet the basic requirement of 1,000 signatures to be on the primary ballot, Woodhams said it is "unheard of" for so many signatures to be valid.

"Certainly people are trying to think of similar instances and no one is coming up with anything," Woodhams said.

So with his congressional career cut short and his White House aspirations extinguished, McCotter, 46, and his campaign staff are now under investigation for fraud.

"We will follow the facts, without fear or favor," Michigan Attorney General Bill Schuette said in a statement announcing the investigation. "If evidence of criminal violations is uncovered, we will not hesitate to prosecute."

If there is s silver lining for McCotter, it's that he personally is not likely to face charges. Instead, his campaign workers who circulated the petitions and signed under oath that the signatures were real could be charged with fraud.

Even without criminal charges, it will be "really difficult" for McCotter to revive his political career after this "personal embarrassment," said longtime Michigan politico Bill Ballenger, now the editor of Inside Michigan Politics.

McCotter told The Hill that the news of the possible fraud "shocked me because it was delegated over to the people who've done it … the last five cycles."

The Michigan Republican declined ABC's request for a comment, but said in a statement that while the signature debacle was "surreal," he took full responsibility.

"Regardless of how the insufficiencies and possible irregularities occurred, the buck stops here with me for the failure to file sufficient petition signatures," he said.

McCotter is no stranger to insufficient shows of support. The GOP congressman's presidential campaign was cut short in September after McCotter failed to get even 1 percent support in a national poll, the minimum requirement to be on stage for one of the first nationally televised Republican primary debate.

McCotter released an unusual campaign video filled with cringe-worthy puns pleading with Fox News, who was hosting the debate, to allow him on stage.

"The voters want to hear new messages," McCotter says, standing in a kitchen during the shaky video.

"If they are not allowed to hear new messages, I think it might leave them with a bit of a saccharine taste in their mouths," McCotter continues, shaking a sugar packet at the camera.

He then holds up a doughnut and says if Fox lets him in, "We can all have a sweet time discussing the issues."

Fox held fast to the 1-percent polling requirement and McCotter did not snag a podium at the Aug. 11 debate leading up to the Iowa Straw Poll. He came in last place in the poll, getting only 35 votes.

McCotter ended his White House bid a month later, telling ABC News that "electability" was the key so "it's not going to be me."

The often long-winded representative ended his congressional re-election bid in a similarly blunt statement.

"I have ended my write-in campaign in Michigan's 11th Congressional District," McCotter said in his Saturday statement. "To those who unhappy at this news, I'm sorry; to those happy at this news, you're welcome."