The unified message coming from both the Clinton and Obama camps is that incrementalism is the only possible path forward and [insert one here: BernieBros, The Kids Today, The Left, Naderites, Silly People Who Never Vote] just don't understand this iron law of politics and should be laughed at. The other message is we would have had the progressive Nirvana if only The Left turned out for midterms.
As for the first bit, well, incrementalism towards what? I can't speak for all [insert one here: BernieBros, The Kids Today, The Left, Naderites, Silly People Who Never Vote], but I imagine that just because people are asking for ponies doesn't mean they expect Benevolent Dictator Sanders to deliver ponies on his first day in office. Maybe some people are that stupid? I suppose. Lots of stupid people out there I guess. But, really, I think for most people ponies are the goal that they'd like politicians to get behind. Maybe providing tax incentives and inner city empowerment zones to establish pony shoe factories (led by Lincoln Chafee, of course), is the best first step to achieving the dream of ponies, but you gotta tell us that the goal is, actually, ponies. Pony shoes without ponies aren't much help.
As for the second part, I've never seen any evidence that The Left (either as an organized (hah) group or just people on that part of the political spectrum) fails to turn out for midterms and that's why Dems lose. Maybe someone could point me to that evidence. It's become an article of faith, something along the lines of "we would have gotten everything we wanted if not for those lazy kids." Or, more bluntly, "fuck'em, they didn't vote for us anyway." What I see every midterm election cycle, and comment on every time, is that the Democrats are determined to run elections about nothing. Keep your heads down, doing nothing but raising money until Labor Day, distance yourself from party ID as much as possible, drop all your money on TV ads which focus on "character" and mostly avoid any policy issue, and then hope that on election night the little roulette ball falls into the right slot and you luck yourself into a congressional seat. Makes the consultants who force this on candidates wealthy. Doesn't seem to win seats or inspire turnout. But, hey, let's blame The Left for not showing up, not the people who get rich losing elections.