From Public Policy Polling:

With his approval numbers hitting new lows it's no surprise that Barack Obama's numbers in our monthly look ahead to the 2012 Presidential race are their worst ever this month. He trails Mitt Romney 46-43, Mike Huckabee 47-45, Newt Gingrich 46-45, and is even tied with Sarah Palin at 46. The only person tested he leads is Jan Brewer, who doesn't have particularly high name recognition on the national level at this point.

Time's new poll has some very different numbers: "Obama clobbered Palin, 55%-34%, in a hypothetical 2012 matchup that should have Democrats salivating." Given the fact that Time's poll is conducted by ABT SRBI, a group I've never heard of, and PPP has a pretty good track record, I think it's safe to say PPP's numbers are a better reflection of reality.