Hillary Clinton was so far ahead, and he had to make up a lot of ground. If you look at the last 16 primaries (unfair to cut it down to 15, since the 3 earliest ones in that bunch were on the same day), Obama won 7 of those contests, Hillary 8, and they drawed in Guam. Hardly losing 14 of the last 15 primaries.
It's true that republicans have demonized the word "liberal" to describe progressives. Paul Wellstone didn't call himself a liberal, he called himself a progressive - which is how it should be. "Progressive" is an actual political movement in the USA going back to the 1800s at least. It's not like some new word that needs a synonym.
