The first GOP debate took place today in South Carolina between Tim Pawlenty, Ron Paul, Gary Johnson, Rick Santorum and Herman Cain (view a bit here). Though many of the debaters make up the GOP's second string, they seem to have brought their A game. Cain, as noted by Pete, seems to have been the breakaway candidate - and Cain doesn't even qualify as a GOP benchwarmer. The sample group featured on Hannity's Fox News slot are sold on Cain, though I agree with Pete that his star will fade.
Of course, none of this really matters yet. My foreign lady is still shocked that we're having presidential debates 18 months ahead of the election, and most Americans probably share her sentiment (mixed with a bit of jaded annoyance). The true significance is simply that the presidential cycle has fully begun.