"You are mainstream Missouri. We want you, Congressman Akin, as our senator, and particularly we want you now because we know that people can't buy you and that you're going to stand up for this state and this country and not be bought by any special-interest group," he said people have told him, at a press conference on Tuesday.

He has until 5 p.m. Central Time on Tuesday to drop out of the race, but he has thus far shown no indication that he plans to do so. In fact, the press conference was the kickoff for Akin's four-day "Common Sense" bus tour, which will bring the embattled lawmaker and a group of high-profile supporters to a number of rallies throughout the state.

Mounting evidence indicates Akin is digging in his heels for what's likely to be an uphill battle even in a state that leans red. He also appeared with former GOP presidential nominee Newt Gingrich at a fundraiser on Monday, and reports indicate he might receive monetary backing from Sen. Jim DeMint's (R-S.C.) Senate Conservatives Fund.

Akin received nationwide attention after comments he made, that pregnancies in cases of "legitimate rape" are rare because "the female body has ways to try to shut that whole thing down," went viral. Reflecting concerns that his continued candidacy would jeopardize an otherwise likely win for Republicans, National Republican groups, including the NRSC and American Crossroads, withdrew funds from the race, and Republican presidential nominee Mitt Romney called for Akin's resignation.

But Akin has persisted, collecting slow but steady support from prominent Republicans like Gingrich and Mike Huckabee. He said on Tuesday that he was "given a trust" by the people of Missouri to replace McCaskill, and portrayed the race as a clear choice between a principled conservative and a staunch supporter of President Obama, whose policies remain unpopular in Missouri.

"A lot of people in politics specialize in asking this question: Can we win? But there is another question that's more fundamental, and that is: What's the right thing to do?" he said.

"When you do the right thing, you end up winning anyway."