The Atlantic has a great piece on the very lucrative side industry of Presidential politics where candidates turn failure into a media career. The best (and worst) examples:
Pat Robertson (1988): His Christian Broadcasting Network and its flagship show, The 700 Club, had been on the air for decades when he launched his surprisingly strong, though ultimately doomed, Republican challenge. (He did finish second in Iowa.) Still, a few months on the campaign trail is always good for ratings and way less messy than blaming natural disasters on devil worship.
David Duke (1998, 1992): Duke actually ran as both a Republican and a Democrat, and while his previous job (as Grand Wizard of the Klu Klux Klan) will forever make him toxic to mainstream TV and radio, he's made a nice living selling books about Jewish conspiracies and can still occasionally be called upon for a convenient (if racist) quote.
Pat Buchanan (1992, 2000): After working in two Republican White Houses and starring as a featured player on the pioneering partisan yell-fests CNN's Crossfire and The McLaughlin Group, Buchanan was a consummate Washington figure, but not very well-known of outside the Beltway. That changed with his first presidential run in 1992, which ended in failure, but led to a fiery convention speech — that introduced America to the phrase "culture war" — and earned him a reputation as one of the more outrageous and unpredictable Republican voices. After his second run in 2002, Buchanan got his own show on MSNBC and even after it was canceled he remained a semi-permanent talking head on the network... before he got fired earlier this year.
Alan Keyes (1996, 2000, 2008): A former diplomat and three-time presidential (and three-time Senate) loser, Keyes also scored his own MSNBC show in 2002, though it was quickly canceled due to poor ratings.
While Pat Robertson isn't exactly brain of America, one would think that he's intelligent enough to know he doesn't have it in him to be President of the United States. And if that's true, you really have to question the motivation of candidates like him. Do they really believe in helping the country, or are they just looking for a TV show? Hermain Cain is probably the best example thus far of a candidate with clear ulterior motives. Sadly, he may have set a dangerous precedent and opened the flood gate for even more idiotic candidates looking for book deals and shows on Fox.