How Hard is it to Actually get in to a Presidential Debate?

Buddy Roemer talks about his exclusion from the Presidential Debates, highlighting a possible problem, yet again, in our electorial processes. Roemer was both a Governor and Congressman but most people have never heard about him (inlcuding myself), partly because he was not involved in any of the debates so far. He talks about the different blocks the sponors of the debates put up to candidates like himself such as reaching a certain percent in national polls and most importantly, he feels, raising certain amounts of money. Roemer says the biggest difference between him and the other candidates is "money and politics."