If you believe the polls, Pennsylvania may be electing a new U.S. senator in a few days.

Of course, the polls could be wrong. Incumbent Republican Sen. Rick Santorum could pull off a stunning come-from-behind victory; certainly, we know that Santorum, and many of his most ardent supporters, believe in miracles.

But Santorum may need a miracle to beat Democratic challenger Bob Casey Jr. Casey has outpaced Santorum throughout the campaign; last week, two new polls showed Casey