Mitt Romney, despite a mediocre showing in two of the first three contests in the Republican primary, has most of the advantages at this point for actually getting the nomination for his party. He is well funded, with tens of millions of dollars and eager donors to back him up, along with the largest SuperPAC in the race thus far. He also has the best ground game of all the Republican candidates, with networks of volunteers in virtually every state. He also has the advantage of being relatively clean as a candidate, meaning if there were any giant scandals in his closet, they likely would have been brought forward by now.
Romney can also take advantage of the tenuous state of the US and world economy, making the case that Obama has failed to help or has hindered the economic recovery. Voters who are frustrated by their economic situation might respond to that. Romney is also strong in some key swing states like Colorado and Nevada, due in no small part to the Mormon population there. He and other Republicans have a huge demographic problem though, as their base of support is whites over 50, and their appeal to the growing percentage of Latino voters is limited at best. This could bring states like Arizona and even Texas into more competitive races.
All that being said, Romney is not very charismatic as a speaker or debater, while Obama most certainly is. The contrast will be hard to ignore or gloss over. Romney has also earned a reputation for switching positions, something that tarnished John Kerry's electability in 2004. He also faces an improving economy, and if unemployment were to fall below 8% by November, his central theme of economic failure on Obama's part would have no punch. It's not that he can't win, he can, but he needs help from the economic situation, or a major series of flubs on Obama's part, for that to happen.
Obama is in a good and improving position. He is sitting on a pile of cash that, unlike Romney, he does not have to spend on the primary election at all, he can hoard it for the battle against Romney in the fall. His approval ratings are not stellar, but not bad either. He is a very motivational speaker and a brilliant campaigner. That being said, the people who do not like him tend to strongly dislike him. He is also a hostage to the economy and because of that, what happens in Europe and elsewhere in the world. These are variables somewhat beyond his control. Iraq could also flare up and become a campaign issue again, or we could be attacked by terrorists. For these reasons, the remaining 9 months to election day are an eternity, and the road to Obama's re-election is not without bumps.