Given that Romney got a lower turnout than McCain, it certainly seems that some number of people have left the party, or are at least witholding support for the time being.

I'll grant you that; but abstaining doesn't help much. They should be splitting the party and separating the real conservatives from the religious right.

That's going to take time- plus I'm not sure they will attain critical mass for a party to succeed. I bet most self-professed 'conservatives' would argue that Republicans are conservative. It seems to be a religion or something.

That's not all too different from Democrats who criticize Obama w.r.t. drone warfare, whistle blower prosecution, etc, but vote for him anyhow.

It's much different; we criticize Obama but don't consider him a DINO and want to kick him out of the party. Republicans tend to eat their own, they want ideological purity in a way Democrats never have. Democrats tolerate ideological differences within the party and within congressional votes vastly more than republicans do.