Obama may have restarted it, using the term un-American to describe policy or actions Democrats oppose. According to Investor’s Business Daily, the use of the term by Democrats goes back to the House Un-American Activities Committee that they’ve successfully associated with Joe McCarthy (R- WI), but was their creation all along.
Now they’re starting to throw the term around again anytime the progressive agenda is endangered.
When Obama reacquired the term for their use Here
Apparently calling someone a racist doesn’t appeal to voters who abandoned the party in droves last November, so their trying something a little more mainstream as a pejorative.