Public Policy Polling is described as a "left-leaning" poll, however even if that is the case I doubt their bias extends so far as to erase a 15 point lead in polls.
Former Pennsylvania Senator Rick Santorum hasn't led a national poll all year, but now that we're eight states into the primary (in which Santorum has won the majority of delegates in three of them) he's finally done in it. Public Policy Polling (D) released their national GOP numbers showing Santorum in first with a huge 15 point lead, besting former Massachusetts Gov. Mitt Romney 38 - 23. Former House Speaker Newt Gingrich, fading in national polling, falls to 17 percent while Rep. Ron Paul (R-TX) gets 13.
While it is delightful, I don't expect Santorum's new-found frontrunner status to last for very long.
Let's not forget that Donald Trump, Michele Bachmann, Rick Perry, Herman Cain, and Newt Gingrich have all lead the polls at one point or another during this 500-lap clown car race.
The only consistent element of the GOP primary has been "anybody but Romney."