Read the full Quinnipiac University poll

Hillary Clinton is already struggling to hold off Barack Obama in next Tuesday’s Ohio and Texas primaries, but if she manages to do that, she looks to face yet another stiff challenge from Obama in the next big state, Pennsylvania on April 22.

Obama has closed to within 6 points of Clinton in Pennsylvania, where she now leads by only 49 percent to 43 percent, according to a Quinnipiac University poll conducted Feb.21-25. The margin of error is 4.4 percent. In mid-February, she had a 52 percent to 36 percent lead in Quinnipiac’s survey and a 44 percent to 32 percent lead in a poll by Franklin & Marshall. Obama’s surge was powered by younger votes in the 18-to-44 age group who now support him over Clinton by 58 percent to 41 percent, a reversal from Clinton’s 52 percent to 41 percent lead in the previous poll.