In this year's marquee race, North Carolina Governor Pat McCrory, a Republican, is fighting for a second four-year term against Democratic challenger Roy Cooper, the state's attorney general.
McCrory has been dogged by the economic backlash against a law he signed in March that restricts bathroom rights for transgender people and limits non-discrimination protections for gays and lesbians.
However, his re-election bid appears to have benefited from his administration's response to record flooding in North Carolina after Hurricane Matthew last month.
"I'm not writing McCrory off," Duffy said in a phone interview.
Most of the other toss-up races are Democratic-held open seats, and they could lead to some surprises.
Republicans may have their best chance at picking up a seat in Vermont, which is expected to vote overwhelmingly for Democrat Hillary Clinton in the presidential race. Republican Lieutenant Governor Phil Scott appears to have the edge over Democrat Sue Minter, a former state transportation secretary.
And in West Virginia, where Republican presidential candidate Donald Trump could get his biggest win, billionaire Democratic businessman Jim Justice has lead in polls over Republican state Senate President Bill Cole.
"There's going to be a lot of ticket-splitting in those races," said Kyle Kondik, managing editor of Sabato's Crystal Ball at the University of Virginia Center for Politics. "It's just a question of how much ticket-splitting there is."
Republicans are battling to defend the governorship in Indiana, which became an open race after Trump tapped Governor Mike Pence as his running mate.
That contest and the open seat in Missouri also remain tight, and Kondik said the Republican gubernatorial candidates could be helped if Trump gained a late boost in support.
"Just like 2014, there really are hard calls that could go one way or another," Kondik said.