Katrina Trinko of National Review summarizes the post Obama announcement polling:
It looks like Barack Obama’s decision to support gay marriage is hurting him in the polls. A CBS/NYT poll out tonight gives Mitt Romney a 3-point lead among voters, 46 percent to 43 percent. A Rasmussen poll conducted after Obama’s announcement on gay marriage gave Romney a 4-point lead. And in the Gallupdaily tracking poll (which is based on seven days’ polling), Obama’s only 1 point ahead today.
Overall, the CBS/NYT poll found that 25 percent of voters are less likely to back Obama because of his new position on gay marriage, while 16 percent are more likely.