There were four tiers of candidates going into the second GOP debate. One candidate who is most likely to get the nomination, two candidates who are serious contenders, four candidates who are long-shots, and those candidates that are negligible.
1) Most likely: Jeb Bush was a clear winner last night as his stock rose from 35% to 40%. Anything that winnows out tested contenders such as John Kasich or Scott Walker is good for Bush.
2) Second tier: Marco Rubio outshined Donald Trump to take a lead in this tier. Carly Fiorina will likely steal some of Trump's poll numbers in the coming week and Trump needs to be really, really solid in the polls to maintain any shot of actually winning in the end.
3) Very Unlikely: Fiorina is still really unlikely win, but certainly lead this group now. Ben Carson will likely give polling to her, as well as Trump, and the outsider voter will solidify with Trump and Fiorina. Walker and Kasich both tumbled into the fourth tier.
4) Negligible: Ted Cruz, Mike Huckabee, Chris Christie, and Rand Paul now welcome Kasich and Walker.
Sources: Betfair, Hypermind, PredictIt, http://twopointoh.predictwise.com/politics/2016RepNomination