Robert P. Casey Jr. (D)

Robert P. Casey Jr. is anything but a typical Democrat. Although he has a liberal economic philosophy and is against the Iraq war, he is also a social conservative who opposes abortion and gun control and favors current limits on embryonic stem cell research.

Nonetheless, when national Democratic leaders were looking for someone to take on two-term incumbent Rick Santorum, the No. 3 Republican in the Senate, they chose Casey, 46. He comes from one of Pennsylvania's best-known political families and had received more votes than any candidate in Pennsylvania history when elected state treasurer in 2004.

In Washington, those used to Santorum will have to adjust to Casey. A native of hardscrabble Scranton and a graduate of Catholic University's law school, Casey is quiet rather than contentious, conciliatory rather than polarizing, and can be so deliberative and self-effacing that he gives new meaning to the notion of political humility.