Corbett is "a known entity: He was attorney general, he's been governor for three and a half years, he has established his public image and it's not a good one," said Chris Borick, who conducts Muhlenberg College's Pennsylvania polling. "For Corbett to, as an incumbent, change the race is going to be a challenge—and up to this point it's seemed he is simply going to be unable to do that."

Following the release of the F&M poll, Corbett's campaign leaked a memo showing the incumbent down just 7 points—far closer than any public polling, but still a sign he's in deep trouble. The Republican Governors Association (RGA) has contributed millions to help Corbett flood the airwaves with ads this summer, but unless the race tightens the group could end up spending its money elsewhere.

On the other hand, Ohio Governor John Kasich, originally expected to face strong opposition, will now coast to a second term in November: Democrat Ed FitzGerald, his opponent, has run one of the worst campaigns of the year, giving national Democrats little hope he can salvage the race. The Cook Political Report earlier this week moved the race to "Solid Republican."

FitzGerald had already struggled to raise money and raise his name ID across the state, both efforts that were completely tanked by a series of damaging headlines about the candidate's conduct. One story said he was found in his car at 4:30 a.m. with a woman who wasn't his wife; another noted that he didn't have a valid driver's license for a decade. Most of FitzGerald's senior staff left in an exodus earlier this month, and remaining staffers have announced the campaign will be shifting its resources toward helping the party's down-ballot candidates in November, a sign of surrender.

Meanwhile, there have been surprises in at least a half-dozen deeply liberal or conservative states, where races that were barely on both parties' target lists are now highly competitive.

Hawaii, for example, is a solidly Democratic state, but unpopular Governor Neil Abercrombie has helped turn the state's gubernatorial race into a barnburner—enough so that the Republican National Committee sent additional staff there and the RGA is likely to spend on former Lieutenant Governor Duke Aiona's behalf.

Abercrombie was defeated in the state's August 9 primary, which gives Democrats hope that their new nominee, state Senator David Ige, can be a clean slate for Democrats this fall. But the combination of bipartisan ire toward the Abercrombie administration and a three-way matchup with Democrat-turned-independent Mufi Hannemann make this a real race.

Republicans point to Colorado and Connecticut as other places they think they'll have a legitimate chance this fall—which, given the organization's plan to spend $100 million in the final 100 days of the campaign, gives them new places to spend that money. Both races feature Democratic incumbents—Connecticut's Dannel Malloy and Colorado's John Hickenlooper—whose approval ratings have declined and who face stronger-than-expected GOP challengers.