Between campaign gaffes, gridlock in Congress and disappointment with government, "everywhere the public turns there's no evidence of competence, and that can be very deeply corrosive," Renshon said. "Anybody who's elected in 2012 is going to have to deal with that, and it's going to be an awfully difficult barrier to overcome."
Public trust in government has been sliding for decades and has never been worse. A CBS/New York Times survey last year found 89 percent of Americans trust the government only some of the time or never.
Princeton historian Julian Zelizer said presidents are forever governing in ways that are at odds with their campaign promises — think of President George H.W. Bush raising taxes despite his "read my lips" pledge that it wouldn't happen, or Woodrow Wilson leading the country into World War I after a re-election campaign with the slogan "He kept us out of war."
But Zelizer said broken promises are often "more accidental or circumstantial" than deliberate.
"Events change," he said. "It's hard for a candidate to predict what will actually happen when they're in the White House."
Obama and Romney, after reminding voters of that truth, must wish they could take an Etch A Sketch and clear the slate.
EDITOR'S NOTE — Nancy Benac has written about government and politics in Washington for nearly three decades.
AP Deputy Director of Polling Jennifer Agiesta contributed to this report.
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