They are not "stuck on Arlen". All incumbents have the right to expect the support of their party. (sometimes it is support in name only.) It's a basic rule of politics. The only time I can think of it not happening is with Senator Smith of NH. But he quit the party briefly earlier in the year. So he gave up any right to expect their support.
The question is how is the GOP supporting Spector? Is it in name only, or are Repub big shots coming to the state to do fundraising for him(against a primary challenger)?
Good question, and I don't know the answer. I did see a news clip (video, Fox News) of Mayor Guiliani standing with Specter, and saying that Specter was the right man for the job. I don't think the context was a fundraiser, but it was an expression of support. Further, I don't know whether the RNC/GOP put Guiliani up to it, or if it was a personal favor (perhaps at Specter's request).
They are not "stuck on Arlen". All incumbents have the right to expect the support of their party. (sometimes it is support in name only.)
I agree with that. Politics is an insider's game. It's hard to get inside, especially against an incumbent.