My equanimity over the possibility that McCain could win -- because he was opposed to torture and Bush's lawlessness -- has been damaged by these latest revelations about his backtracking on earlier opposition to the Bushist excesses.
Greenwald details them here: http://www.salon.com/opinion/greenwald/2008/06/06/mccain/index.html
The bottom line, however, is that we will need to have a change of party in order to really start cleaning house. Is this because the Democrats are more virtuous than the Republicans? No, not really. There's little evidence for that. Indeed, the worst of the Bush excesses would not have been possible without enabling from the so-called opposition party.
But, while no better than the Republicans, the Democrats have incentives to cast the GOP behavior in a bad light and there is therefore a chance that some of the worst can come to light and reforms put in place as the Democrats try to capitalize on the disgust the truth will provoke.
McCain, while personally not as bad as Bush, cannot make the kind of break needed. For one thing, any McCain administration will, naturally, be filled with Republicans, many of theme the same folks that have been responsible for the abuses for the last eight years. But even the ones who did not bear direct responsibility for abuses will have little incentive to reveal the bad behavior of other Republicans.
No, McCain will not do. I'm sure torture will end and the worst abuses of FISA may very well stop under McCain, but it will be a temporary reprieve, easily reversed in the future bad precedents will be allowed to stand and Americans will not trust their government. An Obama administration, on the other hand, provides the opportunity for repudiating the Bush errors, revealing them for the world and America to see, and making clear to everyone how badly we strayed off course. It may not be possible to repair all the damage Bush did, but we can make a start.
Perhaps, someday, the Republicans and the "conservatives" will come to understand where they were wrong and it will be possible to entrust them with power again. Or, perhaps, the Democrats will screw up even worse than the GOP (they certainly have the talent) the voting for the Republicans will seem to be the lesser of the evils.