John Harwood writes in the New York Times:
In the battleground state of Ohio, where Mr. Kerry lost the presidency to George W. Bush, the 2.74 million votes he received almost precisely matched Mr. Obama's 2008 total. Mr. Obama won because John McCain received 300,000 fewer votes than Mr. Bush did. That points to a cautionary reminder for Mr. Obama and his team: the election turned partly on what they did right, but also on what Republicans did wrong. And there is no assurance that Democrats will confront a similarly star-crossed opposition in elections to come.