This has everything to do with Arlen's political survival (aka pulling a Lieberman) as he was about to be voted out of office in the Republican primary there.
And I'm not sure that it's a clear cut win for Democrats... Arlen will be an uncertain ally at best, and negates the Democrats ability to run someone really far to the left against Toomey in PA which I'm sure they would have loved to do. So, a mixed bag. Arlen's effectively been a democrat (or at least not a republican) for many years now anyways, so while this is a PR blow to be sure it won't change much as far as senate politics are concerned.
As far as Arlen trying to say the GOP has moved right since Reagan's days? Hogwash, they've moved left and become indistinguishable from Democrats which is why they're being punished by the voters. Arlen's own appeal to Reaganism is offset by a quote from the man himself:
"A political party cannot be all things to all people. It cannot compromise
its fundamental beliefs for political expediency, or simply to swell its
numbers. It is not a social club or fraternity engaged in intramural contests
to accumulate trophies on the mantel over the fireplace...No one can quarrel
with the idea that a political party hopes it can attract a wide following,
but does it do this by forsaking its basic beliefs? By blurring its own image
so as to be indistinguishable from the opposition party?"
Personally, I'm glad Arlen made his selling out official. Republicans may be down and out right now, but the path back does not involve selling out our principles.
K go ahead and mod me down now. :-)