Liberal Vs. Progressive

LIBERAL vs. PROGRESSIVE....Ryan Sager singles out this as a "bright moment" from the YouTube debate on Monday:
Clinton's forthright disavowal of the term "liberal," because Republicans have made it a dirty word in the minds of voters. She may have just put that term entirely in the past (at least in its Ted Kennedy-bashing usage) and formalized the switch to "progressive."
I only bring this up because it's been in the back of my head for a while that he's right. I've always been vaguely in favor of refusing to give up the "liberal" label because I don't think we ought to let Republicans decide what we can and can't call ourselves, but over the past year or so I've been slowly coming to the conclusion that not many people agree with me about that. I'm a fairly hardnosed descriptivist in vocabulary matters, and it's starting to look like "progressive" has won this battle whether I like it or not. Comments?