By a 59% to 32% margin, most Americans think Barack Obama will win re election if Mitt Romney is the Republican nominee, according to a survey conducted March 7-11. This margin expands significantly if Rick Santorum is the GOP nominee (68% predict an Obama victory, compared to just 24% for Santorum).

Confidence among Democratic voters is high regardless of the outcome of the GOP primary contest. In a hypothetical general election, 83% of Democrats and Democratic leaners predict an Obama victory over Romney and 89% predict a victory over Santorum.

But Republican voters are less confident, particularly if Santorum wins the nomination. By a modest 60% to 30% margin, most Republican and Republican leaning voters think Romney would win in the fall if nominated. But if Santorum is the nominee, about as many Republican voters think Obama would win (43%) as think Santorum would win (46%).

This difference is driven by supporters of Mitt Romney, most of whom (59%) think Obama would win if Santorum is the nominee. By contrast, Santorum’s primary supporters are mostly optimistic about beating Obama regardless of whether Romney (61%) or Santorum (64%) becomes the nominee. Read More

Russell Heimlich  is a former web developer at Pew Research Center.