Sen. Barack Obama still trails Sen. Hillary Clinton in polls leading up to Tuesday’s Pennsylvania primary, although her lead in the Keystone State does not appear to have budged since “Bitter-Gate” became a huge media story.

A composite average of seven polls, all taken in Pennsylvania between April 8 and today, gives Hillary a small, but significant edge of 6.7 percent.

Throw out the two outliers - Obama leads by 3 percent in one poll, Clinton by 14 in another - and the other seven all show 4-9 percent Clinton leads.

At the same time his Pennsylvania prospects appear increasingly slim with time running out, Obama appears to be widening his advantage over Clinton in national polls involving the two Democratic presidential candidates.

An ABC News/Washington Post survey shows a 10 percent advantage for Barack Obama, 51-41. A new Reuters/Zogby survey shows a similar 51-38 edge.

In fact, the smallest lead Obama has over Clinton in national surveys since April 10 is seven percent (48-41), as seen in a Rasmussen tracking poll.

At the same time, both Clinton and Obama continue to poll more or less even with Republican Sen. John McCain in national surveys, either leading or trailing slightly, but within the margin of error on many occasions.

Tonight, the Democrats square off in a Philadelphia debate - the first head-to-head clash in nearly two months, and one that will likely draw the largest audience of the political season to date, given heightened stakes and recent controversy.

Neither candidate was in the Philadelphia area yesterday, but the spouses were, with former President Bill Clinton campaigning in Coatesville, Phoenixville and Quakertown, and Michelle Obama speaking at Haverford College.