A meaningless statement, because the Democratic Party is not a liberal party. It is a centrist party that occasionally leans liberal. Calling it a liberal party is a joke in countries that actually have a strong liberal movement. In a country where the range of mainstream political opinions is not restrict from "slightly-left-of-center to extreme right," the Democratic Party would be considered a conservative party.
Then what does it say that not a single democrat in the house voted for the presidents budget plan?
I don't know. What does it say?
That he is either so far left he's lost his own centrist party, or he has retreated to so much of a centrist position that he isn't left enough for his own party. Either way, he's lost the support of his party so much they don't even want to be shown as being on record for his budget.