I think all your points about Laura Ingraham are very well taken. My own impression is that this is just Laura's MO - throw the Republican under the bus in order to get some quick brownie points and show you're "objective" - then backtrack if the tide turns too much in the other direction.
She used this tactic on Dick Cheney, Donald Rumsfeld, Bush (after Katrina) and now Denny Hastert.
I won't listen to her any more because I think she's a backstabber and an opportunist, or else just plain dopey.