Centrist always dismiss progressives as unpopular and losers who can;'t win a presidential election but the fact remains the last time a true progressive was given the chance as the dem nominee
to run for president in FDR, he was so dominant that the US literally created presidential term limit just to stop his insanely dominant run.
Until someone like Bernie or Warren or AOC actually makes it out of the primary and actually run against republican for president, the whole "progressive can't win" is nothing but conjecture not grounded in facts.
It's a catch 22, progressives can't make it out of the primary because the media and dem establishment have convinced majority of the primary voters that only a centrist/corporate dem can win and you can't know that for sure until you actually put it to the test, so until a progressive lose a presidential election to GOP candidate in the general, it's moot.