Almost two weeks after President Obama announced his support for same-sex marriage, polls provide some measure of the impact -- zero.
Gallup's tracking poll average for May 1-7 -- the period that ended with Vice President Biden's statement that he supported same-sex marriage -- showed Mitt Romney ahead of Obama by 3 points -- 47 percent-44 percent. And the tracking poll average over the past seven days? Romney ahead of Obama by 3 points -- 47 percent-44 percent. In between, neither candidate's standing in the poll changed in any significant way.
Some caveats are in order. It's possible that a national poll might miss subtle shifts in individual states. For example, if Obama lost ground in conservative Southern states and gained ground in more liberal coastal states, and if the changes in those two sets of states canceled each other out, the national numbers would remain unchanged.
A very small shift in one or two swing states could make an important difference in the election outcome but still not register on a national tracking poll. Unfortunately, there aren't very many recent public polls of swing states, so a "before" and "after" comparison isn't possible so far.
A tracking poll also doesn't measure voter enthusiasm. So perhaps some younger voters who favor same-sex marriage rights might have become more motivated to go out and work for Obama, for example, or maybe some conservative voters who already had planned to vote for Romney might have become even more firm in their convictions.
Still, the flat line on the poll average should be a good reminder that events that loom large in the day's headlines often don't have much impact on election results.
The reason for that isn't complex: In elections with an incumbent president, most voters lock into position pretty early, while those who remain persuadable one way or the other generally focus on issues that directly affect their lives.
In this election, that will mostly mean the state of the economy.
Analysts said that the poll numbers did provide some indication that among the small group of people who had shifted their views on gay marriage in the week after the president's announcement, blacks were more likely to shift toward a pro-gay-marriage stand.