Obama for America, "527"

What it says: "Five hundred and thirty seven. The number of votes that changed the course of American history ... If you're thinking that your vote doesn't count, that it won't matter. Well, back then, there were probably at least 537 people who felt the same way."

What it means: President Obama consistently leads Mitt Romney among registered voters but not among likely voters. This ad hopes to scare complacent Obama supporters into voting by invoking the 2000 election. 

Who will see it: Voters in Colorado, Nevada, Iowa, Ohio, New Hampshire, Virginia, Florida, and Wisconsin.