Several commentators have argued persuasively that the democrats and the GOP act as a ratchet mechanism.
The republicans push the envelope with new programs considered extreme. The democrats solidify and systematize these programs.
Not literally true in every instance, but it happens often enough that it appears to be a quality of the system.
That is to say, Obama WON'T push to legalize cannabis, and it's far more than the cult of Reagan in the GOP that keeps the DEA alive and radical.
Here's a blog from which I got the idea:
http://whoisioz.blogspot.ca/2010/05/ratchet-effect-part-infi...
Note: This looks like some obscure blogspot blog. Not so. Who Is Ioz was actively read by all major political bloggers circa 2006-2011. Glenn Greenwald (of recent Edward Snowden fame) commented there a few times.
The blog was not much discussed, as it was considered too radical (or too lucid), but Ioz correctly predicted that Obama would entrench Bush's policies, rather than reverse them.
I have no idea who Ioz is, or what he's doing now.