It is still too early to be sure, but it seems very likely that Mitt Romney will win the nomination.
One reason for this is that he is the only serious candidate who is relatively moderate. This means that primary voters who want a somewhat moderate candidate have no choice but to vote for Romney. Voters who want a more conservative candidate have many people to choose from. In particular right now, they can choose among Cain, Paul, and Perry. This means that these candidates are likely to split the more conservative vote. This will allow Romney to have a much easier time winning.