It's not just Todd Akin. The fallout from the Missouri Senate candidate's "legitimate rape" comment was the latest signal that the Republican path to the majority in the Senate may have just gotten tougher.
Democratic prospects have improved in states where Republicans had long been favored, like North Dakota and Arizona. And Republicans also now face the possibility of losing a seat in Maine.
The GOP argues that it still has a strong path to power, given improved prospects in states like Wisconsin, Nevada and Connecticut.
On Capitol Hill, Republicans are expected to keep control of the House and need to gain four seats claim the Senate majority— or three if Mitt Romney is elected, making Wisconsin Rep. Paul Ryan the tie-breaking vote.
Which party controls the Senate has vast influence over the future of major policies, such as President Barack Obama's health care law and the tax code, as well as the makeup of the Supreme Court. Four of nine current justices are over the age of 70.
If Republicans win control of the Senate and hang onto the House majority, a second-term Obama would find it difficult to pass any major legislation without great compromise. On the other hand, if Republican Mitt Romney wins and the GOP controls Congress, Romney could have an easy time pushing through his agenda to repeal Obama's health care overhaul and Wall Street regulations.
Multiple factors appeared to be working in Republicans' favor as this campaign cycle began. One-third of the Senate is up for grabs every other year, and this year, Democrats have 21 seats to defend, while Republicans have just 10. A still-sluggish economy, high unemployment and a Democratic president with an approval rating under 50 percent offered the GOP reasons for optimism.
But the Senate terrain now looks less dreary for Democrats.
The latest blow for Republicans came Sunday.
Missouri Sen. Claire McCaskill, widely regarded as the most vulnerable Democrat up for re-election this year, watched her opponent, Rep. Akin, start to implode when he said in an interview that women's bodies can shut down pregnancies in cases of what he called "legitimate rape." Although Akin repeatedly apologized, top Republicans demanded he drop out and vowed to deprive him of funds should he stay in the race, as Akin has vowed to do.
That episode came six months after the surprise retirement announcement from Sen. Olympia Snowe, a popular Republican in left-leaning Maine. It created a major opening for Democrats, who were favored to pick up the seat until Angus King, the state's independent former governor, entered the race. Although King has refused to say which party he will caucus with if he wins the seat, both parties expect him to cast his lot with Democrats, making it a loss for Republicans.
In other states, the GOP shifts in fortune have been more subtle.
Democrats are playing defense in North Dakota, where Sen. Kent Conrad is retiring.
The state's other Senate seat and sole House seat both flipped from Democratic to Republican in 2010, and conservatives have been bullish about GOP Rep. Rick Berg's prospects for completing the clean sweep. But even Republicans acknowledge the race has become more competitive, with the GOP outside group Crossroads spending more than $700,000 on ads hitting Democrat Heidi Heitkamp, a huge amount in a state where advertising is relatively cheap.
Heitkamp, a former state attorney general, has eschewed her party's label by criticizing Obama whenever opportunities present — on domestic energy, for instance, a hot issue in North Dakota. Berg has relentlessly pinned Heitkamp to Obama and his health care law, both of which are unpopular there and which Heitkamp praised before launching her campaign.
In Arizona, Republican Rep. Jeff Flake was expected to coast to a seat left open by the retiring Sen. Jon Kyl. But real estate mogul Wil Cardon has pummeled Flake on the airwaves, spending $6 million of his own money on mostly negative TV ads.
Flake still is the heavy favorite in Tuesday's primary. But if he wins, he'll enter the general election with just $1.7 million in the bank, slightly less than Democrat Richard Carmona. A former U.S. surgeon general and son of Puerto Rican immigrants, Carmona has Democrats enthused over his perceived appeal to independents and the state's growing Hispanic population.
"There's far too much extreme, vitriolic attacks," Carmona said on Friday, "and I think the public is tired of that."
Republicans have seen their prospects brighten elsewhere in recent months. And they say they're nimble enough to redirect their resources to achieve maximum effect.
"Missouri is clearly a setback if Congressman Akin chooses to remain in the race," said National Republican Senatorial Committee spokesman Brian Walsh. "On the flip side, Republicans still have a number of great opportunities to win back seats in other states across the country."
Wisconsin Republicans have their most viable general-election candidate in former Gov. Tommy Thompson, who edged out three conservatives with closer ties to the tea party in a hard-fought August primary. A CBS-New York Times poll released Thursday showed Thompson 6 points ahead of Rep. Tammy Baldwin, one of the House's most consistent liberals. And GOP enthusiasm may be higher in Wisconsin now that Romney has tapped Ryan, one of the state's congressmen, as his running mate.
To the west, Nevada Rep. Shelley Berkley, the state's Democratic Senate nominee, is under investigation by the House Ethics Committee. For Berkley, it's an inopportune time for the panel to be examining whether she used her position to benefit her family's financial interests. Berkley has said there was no conflict of interest.
Republicans are also eyeing opportunities in Connecticut, where former wrestling executive Linda McMahon is making a second go at a seat after losing in 2010, and in Florida and Virginia. Those two presidential battlegrounds have competitive Senate races likely to be overshadowed by the deluge of spending by Romney and Obama.