Absolutely! There have always been pockets of voters that will vote progressive.
Progressives always bring up Vermont and say, "see, not all White people are racist fuckheads, in Vermont they voted for Bernie". Same with AOC who has a tiny district in NYC that is majority-minority.
In the right place, under the right conditions a Progressive candidate can win.
That doesn't change the basic overall dynamic. 42% of the country, 2 out of 3 White voters, votes Trumpublican. That's the reality the Democrats have to deal with.
So, do you want to have voice in what goes on? Or are you content to "be pure to your ideas and win in your tiny fishbowl, while losing overall every time".
Until 2015, Bernie was a fucking "back bencher" who never got anything passed. A 30 year career that consisted of bringing home defense contracts for his state and being a professional critic of what everyone else did.
"All Politics is local in the end" so if you are in one of the "magical places" where Progressives can get elected, that's great for you. The rest of us have to live in the country were 2 out of 3 White people are racists fuckheads with guns, who are looking for an excuse to start shooting us.
We cannot lose an election to them right now.
In ten years, when some of the Boomers die off and the national demographics look more like California (where Whites are the biggest minority) then I will be happy to vote for a "doomed Progressive" candidate. Right now, when these White voters want to create an Apartheid state so that they never lose another election, WE NEED TO BE UNITED TO PREVENT THAT.