Rasmussen daily presidential tracking poll for 5/12/12
Romney 50%, Obama 42%, third party 4%, undecided 3%.
The Rasmussen poll is the only major poll which surveys only likely voters, as opposed to registered voters. This has two consequences. First, Rasmussen polls consistently show Republican candidates doing better than other polls do- or, perhaps more accurately, shows Democratic candidates not doing as well. The reason is that Democrats and Democratic-leaning voters are less likely to actually vote than Republicans and Republican-leaning voters.
The second consequence is that the results of final Rasmussen polls generally more accurately predict the actual results of elections than do the other polls.