With Arlen Specter getting his Democrat (back) on, the Republican primary field in PA was largely ceded to Pat Twoomey, who gave Specter a run for his money in 2004. Now that Specter's gone, it looks like Tom Ridge is considering a run for the Senate. Governor for eight years, first Secretary of Homeland Security, Ridge is a known name in Republican circles and has already demonstrated statewide electability.
I'd welcome a primary battle between Twoomey and Ridge. Twoomey's a bit ideological for Pennsylvania, and Ridge is a bit soft for me. I think a primary would expose certain elements of each's political mien, and ultimately would cause each to review some of what makes them less electable. The candidate who emerges would have a much better shot at beating Specter than an unopposed Republican.