Nate Cohn writes the Electionate blog for The New Republic.

From the moment political reporters armed with leaked internal polls wrote that Obama led by mid-to-upper single digits in Ohio, the Buckeye State was widely regarded as Romney’s Achilles heel. As early as mid-August, the conventional wisdom held that some combination of attacks on Romney’s tenure at Bain, the auto bailout, the shale gas boom, and a strong local economy was allowing Obama to overcome his national weakness with white working class voters in a traditionally Republican state.

When Obama’s national standing faltered after the first presidential debate, polls showed Obama falling behind in the “new coalition” states while maintaining a slight but consistent lead in the key Midwestern battlegrounds, including Ohio. The president seemed to be defying gravity, and the Obama campaign told reporters that Ohio was the crux of the “midwestern firewall” that provided the president with a critical and durable advantage in the Electoral College. With the polls showing Obama ahead by 3 points with more than 49 percent of the vote, the state appeared poised to provide the president with reelection....