From William Jacobson's blog:
a full blow investigation and hearings will turn mostly on what the Democrats knew, and when they knew it. The Republicans mostly couldn't care less if they were "blamed" for keeping the country safe even if it necessitated waterboarding the mastermind of 9/11 to prevent further attacks. When faced with sacrificing a city versus using harsh interrogation methods, most voters would opt for harsh interrogation.
That the Democrats have more to lose is demonstrated by the looming fight between Democrats in Congress and the CIA. The Democrats are complaining that the CIA is out to get them through selective leaks of documents. These are the same Democrats who cheered when the CIA leaked information damaging to Bush administration policies. So that complaining is going to go no where
( To read more of Mr Jacobson's analysis click on the title for a link)