President Obama's approval rating in the key swing state of Pennsylvania stands at just 42 percent, according to a new poll out Tuesday.

New numbers from Democratic-leaning Public Policy Polling show a majority of voters disapprove of the job Obama is doing and found the president in a dead heat with three potential Republican opponents. The numbers are a far cry from 2008 when Obama easily bested Sen. John McCain (R-Ariz.) in the state.

Obama's statistically tied with former Massachusetts Gov. Mitt Romney, former Arkansas Gov. Mike Huckabee and former Sen. Rick Santorum (Pa.). Obama leads Huckabee 45 percent to 44 percent; Santorum 45 percent to 43 percent; but trails Romney 43 percent to 42 percent. 

Should either former House Speaker Newt Gingrich (Ga.) or former Alaska Gov. Sarah Palin win the Republican nomination, however, the poll shows Obama beating them both handily. The president leads Gingrich 47 percent to 39 percent. He leads Palin 50 percent to 39 percent. 

The trouble for Obama comes with independent voters and white Democrats. In all, 54 percent of self-identified independents disapprove of the job the president is doing, compared to just 39 percent who approve. Among white Democrats, just 64 percent approve. That's compared to 86 percent of black Democrats who approve.

"Those numbers suggest that a lot of the voters who fueled Hillary Clinton's primary victory in the state and then sucked it up and voted for Obama in the general election the last time around haven't been real thrilled with what they've seen from him so far and could split their tickets next year — if the Republicans put up someone who's seen as a reasonable alternative," wrote pollster Tom Jensen. 

Overall, just 68 percent of Pennsylvania Democrats approve of the job Obama is doing. That's well below the 86 percent approval PPP found among Democrats nationally.

The survey polled 593 Pennsylvania voters and has a margin of error of plus-or-minus 4 percentage points.