One defining issue?
Babette Josephs, a rare progressive State Rep. from the Philadelphia region, has spoken in support of Casey, citing past encounters around supporting women's shelters, labor rights, and other old-fashioned liberal causes, as well as his work to fund daycare and maintain access to contraception, even when then-Governor Ridge's policies made such things difficult. She also said that he intends to have no abortion-related litmus test for judges, being more focused on finding "folks who aren't interested in repealing the entire New Deal."
I hope that in the course of the next year and a half, we can in some degree get past coverage that focuses on the Democratic party's internal wranglings about the (never-to-be-settled) abortion question and can hear about some of the other issues facing potential Senators. Further, I hope that Casey can develop some proactive positions that will give voters something to vote for rather than just against. Remember that Casey only announced a few weeks ago; there must be time to learn more.