The Republican Party has historically leveraged the subject of abortion far more effectively than Democrats. This year, it could cost them control of the Senate.

The Senate has been up for grabs since the beginning of the cycle. Democrats currently control 53 seats, including the two independents in their caucus, but are defending 23 seats to just 10 on the Republican side. The possibilities are multiplied by uncertainty over who will wield the tie-breaking vote—Vice President Joe Biden or Rep. Paul Ryan—and which party Maine independent Angus King will shack up with in the likely event that he wins.

Two major blows have befallen the Republicans since August. First, Todd Akin's campaign imploded over his statement that women rarely get pregnant from "legitimate rape." Now, Senate candidate Richard Mourdock in Indiana is watching his luck nosedive after stating that "even when life begins in that horrible situation of rape, that it is something that God intended to happen." Under the Signal's prediction model, his odds of victory have plummeted 50 points in 36 hours.

Sources: Betfair, Intrade, HuffPost Pollster, RealClearPolitics

Establishment Republicans did not want either candidate on the ticket in the first place. We considered Indiana a safe Republican hold prior to incumbent Richard Lugar's loss to Mourdock in the primary. Akin knocked off a six-term congressman backed by Sarah Palin in the Missouri primary, to the delight of the Democratic incumbent, Sen. Claire McCaskill.

We switched Indiana to a possible pickup for Democrats earlier this month, but at the time it had the longest odds for Democrats of the five Republican-leaning seats still in play.

There's a lot of daylight between these two suffering campaigns. While Akin's claim represents a fringe, discredited theory about rape and pregnancy, Mourdock's position finds support among some in his party. The Republican Party's platform does not mention rape or incest when discussing abortion, and Rep. Paul Ryan has stated that "the method of conception does not change the definition of life" (though he dutifully defers to Romney's more moderate position now that he's on the ticket). Slate estimates that 12 to 15 of the 33 Republican senatorial candidates share this position.

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A majority of Americans continue to believe that abortion should fall in the area between always legal and always illegal. Curiously, while public opinion on this point has not shifted much through time, polls have found that Americans are now more likely to identify themselves as "pro-life" than "pro-choice." Mourdock's statement is damaging not because it is factually incorrect, like Akin's, but because it exposes rifts among abortion opponents that no pragmatic Republican should want surfaced in this election.

Follow the state-by-state and overall senatorial predictions in real time with PredictWise.com.

David Rothschild has a Ph.D. in applied economics from the Wharton School of Business at the University of Pennsylvania. Follow him on Twitter @DavMicRot.