William A. Galston is a contributing editor for The New Republic.

The emerging conventional wisdom among many Democrats takes the form of two equations: 2012 = 2004, and Bain = Swift Boats. There’s also a supporting narrative: The negative campaign against John Kerry fatally weakened his candidacy, securing the victory of an incumbent who could not have won based on his own record. And so, the idea goes, a president whose performance the public doesn’t much like can power his way to a narrow, less than pretty win by eviscerating his challenger.

But the evidence in favor of all of these propositions is remarkably thin. The basic structure of the 2004 campaign differed fundamentally from the one we’re now enduring. The available evidence suggests that even in the short-term, the attacks on Romney have been measurably less successful than were those on Kerry. And Obama’s supporters seem to have forgotten that the reason Bush prevailed was because enough Americans ended up approving of his record and leadership in the areas they cared about the most.

In 2012, there is a single dominant issue—the economy. The people are trying to decide whether Obama has managed our economic challenges well enough to deserve another four years and, if not, whether Romney’s economic experience and plans make him an acceptable alternative.

In 2004, by contrast, there was no single dominant issue...