Independent political groups have long been the guerrilla warriors of presidential elections, tossing explosive advertisements into the middle of a campaign like hand grenades, with little regard for the strategy of the candidate they support.

But this year, in a tight race that leaves very little room for error, the conservative “super PACs” and other outside entities working to defeat President Obama have reached a consensus: Going off message is simply too risky.

So they operate largely from the same playbook, sharing polling data and focus group research to develop many of the same lines of attack. And they are being careful to keep their efforts consistent with the themes being emphasized by Mitt Romney’s campaign.

The result is a striking degree of symmetry. To see many of the anti-Obama ads that have run on television recently, it would be easy to conclude that they were made in the same studios, by the same producers working for the same campaign.