The Paradox Of Change
To even get started, we have to assume that Obama wants to change the country in a progressive direction. This, of course, is a patent falsehood. But we'll assume it for the time being.
There are two aspects of progressive change: substantive and procedural. Substantive change means things like withdrawing troops from Iraq and limiting greenhouse gas emissions. Procedural change involves change in how our government is run, most notably the excessive power claimed by the presidency over the last eight years.
Obama will have to work with a center-right Congress, not too different from the one we have now. That Congress will seek to stymie any substantively progressive measures that come through -- for example, a climate change bill would be so watered down by the time that it reaches Obama's desk that the ecological footprint of the ink he uses to sign it could well outweigh the bill's actual impacts. That means the only way he can create any real substantive change is to do an end-run around the legislative process, claiming authority as The Decider to do whatever he wants.
In other words, achieving substantive substantive change would require abandoning (or even working contrary to) procedural progressive change. And achieving procedural progressive change would destroy his ability to achieve substantive progressive change.