When that power has been created by freak conditions. The current metastasized cancer that is the Bush administration was created by the two freak storms of the stolen 2000 election and 9/11, the latter of which made the country bat shit crazy in a way that was almost indescribably bad, but that's for another post. Now Bush is out of there, or at least will be soon enough, and the perfect storm that created his authoritarianism is coming apart. Even if McCain, as is likely, tries to maintain the Bush rhetoric and Bush agenda, he won't be able to do so fully because he won't have the legitimacy of being the '9/11 President' . McCain also has his own spin on this stuff, largely because he has a brain and isn't as stupid as a box of rocks, his epitaph for Bush in 2000.
This opens up opportunities for opposition that haven't been there since 9/11. The armor of McCain, if he wins, isn't as invulnerable as that around Bush and public opinion and protest will probably be able to have more of an effect on his administration.
That said, McCain wants to seriously expand nuclear power plants and said that he would be in Iraq for a thousand years if that's what it took to get some sort of 'victory'.
But the time is running out on Bush, and as he gets more and more impotent I'm sure he'll see more demonstrations by leaders in the international community of just what they've been thinking of him all this time, but have been cowed from saying openly because of the power of the U.S.