The balance of enthusiasm favored Republicans and conservatives in 2010, as it had favored Democrats in 2006 and 2008. It could conceivably shift and favor the Democrats once again.

Another factor is that polls show that most Americans have favorable personal feelings toward the president. Bill Clinton and George W. Bush both happened to have personal characteristics that people on the other side of the cultural divide absolutely loathed. Obama doesn’t.

His reliance on his teleprompter, his secret smoking, his irritability when not adored — these are pretty minor failings. People like his family and his obvious devotion to them. They don’t mind that he likes to get away and play golf or shoot hoops from time to time.

Then there is the powerful desire Americans have to see their presidents succeed. That worked for Bill Clinton in 1996 and George W. Bush in 2004. Polls and focus groups showed that voters in the middle of the political spectrum were ready to overlook their weaknesses and appreciated their strengths in those years. That could be the case with Obama in 2012.

Moreover, there will be a reluctance on the part of many voters, understandable in light of our history, to reject the first African-American president.