A week after President Obama won re-election, two themes are dominant. First, that Mr. Obama kept his job because key elements of his base—notably young people, African-Americans, Latinos and Asian-Americans—turned out for him. Second, that the growing size of these voting blocs represents a decisive challenge for the Republican Party.

Both points are true, but most observers are overstating the gravity of the GOP’s problem. In particular, they are paying too little attention to how weak a candidate Mitt Romney was, and how much that hurt Republican prospects. …

Surprisingly, Mr. Romney proved unable to exploit Mr. Obama’s biggest weakness: the economy. Seventy-six percent of exit-poll respondents rated the national economy “poor” or only “fair,” and just 25% said their finances were better off than they were four years ago. …

Despite their weak candidate, Republicans increased their share of the presidential vote among many major demographic groups. Compared with 2008, they made significant gains among men (four percentage points), whites (four points), younger voters (six points), white Catholics (seven points) and Jews (nine points). Mr. Romney also carried the independent vote 50% to 45%. Four years ago, independents voted for Mr. Obama 52% to 44%.