Here's a set of numbers showing a remarkable trend -- in battleground states, Obama consistently does best in surveys from the left-leaning Public Policy Polling group.
Via Real Clear Politics' average of polls, I checked out the last two months of surveys in each battleground state.
In 11/13 states, Obama picked up his best scores in PPP polls (two of those were ties between PPP and another polling group).
OHIO = PPP shows Obama 50% Romney 43%.
FLORIDA: PPP Obama 50% Romney 45%.
VIRGINIA: PPP: Obama 51% Romney 43%.
NEW HAMPSHIRE: PPP: Obama 53% Romney 41%.
PENNSYLVANIA: PPP and Quinnipiac both showed Obama up 8%.
MICHIGAN: PPP: Obama 53% Romney 39%.
WISCONSIN: PPP is not the most favorable poll for Obama.
IOWA: Only two polls in last two months. NBC News had a tie; PPP had Obama up by 10%.
MISSOURI: Only two polls in last two months. Rasmussen had Romney up 3%; PPP had Obama up 1%.
COLORADO: PPP: Obama 53% Romney 40%.
NEVADA: PPP and Rasmussen tied for biggest Obama lead.
ARIZONA: PPP showed Romney leading by more than the RCP average.
NORTH CAROLINA: PPP: Obama 49% Romney 44%.
In nearly every case, PPP had Obama scoring higher than the RCP average.
Granted, this is over a two-month time period, and there can be variability in state polling, but it's an awfully consistent phenomenon.
Simply put: Obama generally does far better in PPP polls than surveys from other firms.
Update: I changed the title of the post to clarify that I'm not charging PPP with anything intentional. I'm merely pointing out an interesting pattern -- Obama tends to do much better in PPP polls than elsewhere.