I should also note that Specter's motives are obvious: He wasn't going to win reelection in Pennsylvania in 2010 as a Republican.
And that's what's really interesting about this from a political perspective. The "industrial" north is also socially liberal. Meanwhile the "rural" south is socially conservative. The Midwest is suddenly swimming to the left, while the West is thinking about it. The West Coast is--at this point--the East Coast without a stick up their ass.
The long term effects of Nixon's South stragity has killed his own party (oh yeah, and W's total lack of ability to do anything right). But there are two important trends as to why Our Father's G.O.P. is dead.
1) The G.O.P. of the 20th century was a party with libertarian roots and fiscal motives. It was a party that wanted the government to stay out of every one's business and lower their taxes. However, this was a poor election formal considering that many people lived through the 1930s and saw, or thought they saw, the effects of the New Deal Democrats. But as the Democrats tore themselves apart in the late 60s, Nixon was smart in thinking that he could pick up the South and flip it from red to blue (even if this happened for racist reasons).
This worked beautifully helping get H.W. Bush elected and then W. in 2000 and 2004 (Reagan didn't need the South all that much). However, to keep the new Southern party members happy, the Republicans had to throw them a bone, and that bone was a greater focus on social issues which lead the party to champion Southern Populist ideas. This anti-intellectual arm of the party turned off many Northeast, Midwest, and West Coast to the point where it's impossible to find a Northeast Republican. (There is probably also an interesting study about Roe vs. Wade and how that eventually would hurt the G.O.P. since a majority of Americans favor the woman's right to choose/abortion rights).
2) But this could only happen if the Democrats changed too. And they did. It took over 20 years, but beginning with Clinton (and before, but he was the sign that things had changed within the party), the Democrats started reading economic text books. Suddenly, Chicago School Economics wasn't evil if one throws in a dash of Keynesian economics and everyone tells unions that they're great. Bing, bam, boom, those who were fiscally conservative, the idea of voting for a Democrat wasn't so crazy. It's not that America has moved to the left, as much as the Democrats began looking to the right a bit.
The G.O.P. is it total disarray. There is no leadership. The party is being pulled five hundred different ways. The anti-intellectual, our way or the high way arm of the party seems to be in control. Moderates (i.e. pro-choice G.O.P.ers) are shunned. The party, right now, is fucked. They better get their act together or else Sarah Palin is going to lead this party to a defeat that only George McGovern could get tell her about.