For all the debate over whether it's fair game for President Obama's campaign to tout the killing of Osama bin Laden and suggest that Mitt Romney wouldn't have ordered the raid, the reality is that the issue is very unlikely to have much impact in the election. As it is, when news of the operation broke one year ago, Obama received a small six-point bounce in Gallup's daily tracking poll that had dissipated within two weeks. In contrast, at a time when national security was a greater focus for Americans, President Bush got a 15-point bump after Saddam Hussein's capture that lasted seven weeks.
That's not to say that the killing doesn't benefit Obama at all. I think it does help Obama inoculate himself against attacks that he's a soft commander in chief. In the 1980 election, American hostages remained in captivity in Iran and a rescue mission had been bungled -- all of which played into the perception of Jimmy Carter as a weak leader, which Ronald Reagan was able to exploit.
However many problems I have with Obama's national security policy, I believe that in the political context, he'll be able to point to the bin Laden killing to help neutralize charges that he's too much of an appeaser. But I don't think he'll be able to get much of an actual boost out of it, because the War on Terror has receded in importance to most Americans.