Missouri Rep. Todd Akin may be the black sheep of the Republican party, but the congressman has refused to drop his bid for the U.S. Senate, despite mounting evidence indicating his campaign is essentially already over.

Ignoring calls from the leaders of his own party, including presidential candidate Mitt Romney, Akin let the final deadline for his withdrawal from the race come and go on Tuesday, when he defiantly held a rally with about 200 supporters and vowed to defeat incumbent Democratic Sen. Claire McCaskill.

Meanwhile, McCaskill is airing a new ad highlighting Akin’s controversial and highly-criticized August interview where he -- attempting to defend his belief that abortion should be illegal for every woman, even rape vicitms -- suggested women who are the victims of ‘legitimate rape’ are somehow biologically incapable of becoming pregnant. Akin, who was leading in the polls before the interview was publicized, is now neck and neck with McCaskill, whose campaign has seen an influx of contributions following Akin’s rape comments.

Akin’s campaign had raised approximately $2.2 million this election cycle and only had about $530,000 on hand as of mid-July, according to the Center for Responsive Politics, which also notes the congressman has received little support from outside spending groups aligned with Republican interests.

Akin, who emerged as the Republican Senate nominee after a tough five-way primary race, primarily benefited from the flood of outside money spent in opposition to his Republican challengers. The McCaskill campaign, as The Sunlight Foundation notes, wanted Akin to be the GOP nominee because he, as a deeply conservative evangelical Christian, was viewed as the least formidable challenger.

The congressman has received no financial backing from the National Republican Senatorial Committee, which issued a statement condemning his rape comments in August and appeared to suggest that Akin rethink his Senate candidacy.

McCaskill, although initially seen as one of the Senate’s most vulnerable incumbents, had raised more than $12.5 million toward her reelection effort as of mid-July, almost six times more money than Akin. McCaskill’s campaign has also received millions in outside support from women’s organizations: NARAL Pro-Choice America has expended at least $1.5 million in support of the senator, while spending an enormous $16.9 million in opposition to Akin.

EMILY’S List, which supports female Democratic candidates, is the top contributor to McCaskill’s 2012 campaign, the Center for Responsive Politics reports. McCaskill, following the Akin debacle, also received financial backing for liberal-leaning organizations such as the Majority PAC, Patriot Majority PAC and Voices from the American Federation of Government Employees.

There is at least one person who has Akin’s back. On Monday, former House Speaker and one-time GOP presidential candidate Newt Gingrich hosted a fundraiser for Akin in St. Louis, in an attempt to replenish Akin’s financially strapped campaign. The cost of attendance was $750 per PAC and $500 per individual.

On Wednesday, two more conservative leaders known for their opposition to abortion rights voiced their support for Akin.  In a statement, former Sen. Rick Santorum and Sen. Jim DeMint of South Carolina called Akin a "principled conservative who is committed to winning and fighting for freedom in the U.S. Senate."

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