Republican Ed Martin, who lost a close race to Rep. Russ Carnahan (D-Mo.), has finally conceded after nearly a week of questioning whether fraud played a part in his defeat last Tuesday. 

Martin initially said an investigation into Tuesday's results was warranted, citing irregularities in a number of precincts. 

Late on election night, Martin had a razor-thin lead over Carnahan, but after the final tally was in the next morning, the incumbent had a lead of close to 4,500 votes.    

"Our team of hundreds of volunteers and thousands of supporters had reasonable reasons to be suspicious," Martin wrote in a message to supporters Monday. "While it would be irresponsible to make accusations that exceed the evidence, there was at the time ample reason to be concerned. Voicing those concerns was a difficult thing to do but I felt it was the right thing to do." 

The Republican said after learning that Carnahan's vote surge came from unreported votes "from the northwest precincts of St. Louis County," and not from precincts within the city, his worry over voter fraud dissipated.     

Martin wrote that "although I have concerns about other incidents and improper conduct on election day, I no longer believe these concerns are sufficient to continue our review of what has occurred or delay agreeing that this election is over." 

Martin said he phoned Carnahan Monday morning to officially concede.