Looking at just the two biggest super PACs most closely associated with the candidates, it’s clear what has the president and other Democrats so worried.
Restore Our Future, the super PAC backing Romney, raised $61 million through the end of May, two-thirds of which came from 50 extremely wealthy donors, according to the Center for Responsive Politics. But it seems likely to raise far more in months to come. Its top donor, Las Vegas casino magnate Sheldon Adelson, who recently gave the group $10 million, has said he may ultimately invest as much as $100 million.
By contrast, the primary Democratic super PAC supporting Obama, Priorities USA Action, raised just over $14 million. Some of that money came from wealthy individuals – the largest single donor was Jeffrey Katzenberg of DreamWorks, who donated $2 million. But a lot also came from labor organizations, many of which have their own political arms.
Here’s where it gets murky: While super PACs are required to disclose their donors, “issue advocacy” groups – such as Crossroads GPS, an offshoot of American Crossroads – are not, making it hard to track all the money being raised that may ultimately have a big affect on the outcome of the campaign.