Other races have flirted with the prognosticators' most-watched list, but the Keystone State's Sixth District has remained one of the nation's closest contests since the beginning. It was no accident, then, that the last national Democratic radio address ahead of the election was given not by a party heavyweight like Howard Dean or Nancy Pelosi but by Gerlach's challenger, Lois Murphy. "We face a clear choice between fear and a new direction for our country," she said, highlighting a Democratic legislative agenda of improving homeland security, raising the minimum wage, cutting interest rates on student loans, and, of course, changing strategy in Iraq.

The Sixth District, which runs from Reading to the fast-growing Philadelphia suburbs, is a mixture of affluent suburbs and rusted former industrial towns. Issues like healthcare and schools top constituent concerns, as well as the war, which has seen many Pennsylvanians sent overseas.

"Attitudes on the war in Iraq will be the thing to watch," says a Republican strategist. "The closer people in the district associate the war in Iraq with the global war on terror, the better it will be for Gerlach and Republicans across the board." Responses from likely voters, polled over the past year, don't show a clear favorite. Turnout in Berks County is likely to be the deciding factor, as it was in the last contest in 2004. Thus far, Murphy has held a slight lead in seven of the nine major polls conducted in the district, the last coming on October 19 and showing Murphy up 49-44 percent, with 7 percent undecided.

—Alex Kingsbury