As much as I dislike Rush Limbaugh, I think he is dead on in his assesment of the Republican party right now. He says the base is fractured, and it absolutely is.
The blame, (or credit depending on who you are), lies with Bush and the neocons. It was astounding to watch them in action, completely ignoring the long term effects of what they were doing. Were they really so dumb that they couldn't see that war in Iraq was a bad idea, or were they so arrogant that they thought they could sell it to us? I think it was mostly their arrogance. Why didn't any Republican try to stop Bush from out of control spending? Why didn't any Republican try to stop him from creating more government beauracracy, (DHS, etc.)? Why did so few Republicans oppose his liberal immigration views? Did the Republicans really fear opposing Bush on all of these things? They must have, because they allowed themselves to be swept out of office in the midterms for refusing to oppose him on the war and immigration. They got what they deserved, a fractured base that will take years to heal, if it ever does.
On the Democrat's side, their only blunder was not being able to stop Bush's war in Iraq. And that wasn't really a blunder, it was mostly an effort that simply failed. They didn't have a large enough majority. Their base didn't fracture like the Republican's did. The Dems are sitting pretty for the future right now, unless they screw it up somehow. The Repubs are in trouble.