Top national pollster Peter Hart believes President Barack Obama will face a very close election next fall no matter which Republican becomes the GOP nominee. He compared the nation’s mood to the election in 1968.

“I just don’t know which way things are going to swing,” Hart told a small gathering co-hosted by the Harvard Kennedy School’s Shorenstein Center and the Institute of Politics last week. “Never have I felt less certain of the outcome than I am with this election.”

Hart, a Democratic pollster, said the challenges facing Obama as he seeks re-election “are indeed great,” but he added that the GOP frontrunners, such as former Massachusetts Gov. Mitt Romney, have their problems as well.

“This is an electorate that is searching,” Hart said of the dissatisfaction that GOP voters say they have with the 2012 field. “It’s like Friday night and you don’t have a date to the prom.”

Hart wouldn’t predict whether Romney would win the nomination, saying that it’s “a story that’s just starting.”

Hart said that the frustration from the American people his firm surveys is “combustible” and that it’s not impossible that voters in 2012 would oust the incumbent parties in the House, Senate and the White House.