If you want to be president these days, it's not enough to have an appealing platform, strong public speaking skills or even to look polished on television. You also have to prove you're at least slightly cool. Blame Bill Clinton for blowing the saxophone on Arsenio Hall in 1992. It's a measure of how important this yardstick has become that both Democratic presidential candidates showed up on Colbert Report last night, plus third-place John Edwards, who has been out of the race for months. Hillary Clinton was funny in a skit in which she fixes a video screen, even if she didn't find the breakthrough moment her husband did in 1992. Barack Obama was a bit more aloof, perhaps strategically so; he not only appeared via satellite but also hewed much closer to his campaign personality than Clinton. Edwards was by yards the funniest, probably because he has the least to lose. Evaluate would-be leaders of the free world on their ability to crack comedy-show jokes after the jump, where you'll find video of Clinton, Obama and Edwards on Colbert.