Polls depend on too many factors to be reliable in the primaries, as past predictions show.
At the moment, Clinton is showing a double digit lead in Pennsylvania. A few brief extracts from Monday's Inquirer. If one is interested, google the Philadelphia Inquirer and search archives.

"Views on Pa. Primary Race Continue to evolve"
"The latest: State is Important but not the clincher."
Philadelphia Inquirer, 2008-03-17; Larry Eichel, Inquirer Senior Writer.

The Clinton campaign, which leads by double digits in state polls, has tried to talk up the state's role, while Obama's campaign manager has called it "only one of 10 remeining contests."
"...Pennsylvania seems to have been categorized in advance as Clinton territory because of her success in demographically similar states such as Ohio, her husband's lingering statewide popularity, and support she has been receiving from the local political extablishment, led by Gov. Rendell and Mayor [Phila.] Nutter.
"The candidates themselves have contributed to such sentiment in word and deed."
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"But the Obama campaign has been sending out signals suggesting that it has not yet figured out whether to go all-out in the state. Which in turnhas caused Clinton's chief stratigest, Mark Penn, to accuse Obama and his aides of "turning their back on Pennsylvania."
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"Obama an company are working hard to register voters before the March 24 deadline. This is a closed primary- another factor that could work to Clinton's benefit- meaning that independents and Republicans may vote in the Democratic primary only if they change their registration in advance."
"Obama's overall lead in delegates......... allows him to afford a respectable loss in Pennsylvania.
But he abandons the state at his peril. The Democrats proportional system of allocating delegates- the same system responsible for making this race so close- forces him to make a serious effort."
"That's because a blowout loss would give Clinton a substantial haul of delegates, make a big impression on the superdelegates, and perhaps create the idea among voters that the campaign has taken a turn.
"In the end, PA isn't going to be downplayed," said Neil Oxman, a Philadelphia-based political consultant not working for either candidate. "This is not Wyoming or Mississippi."