Democrats have long found the flip phone Chuck Schumer still insists on using as an endearing quirk that illustrates how committed he is to his way of talking to all sorts of allies, all the time.

In failing to demonstrate what they stand for, Democrats fumbled the chance to show why they deserve a return to power, centrists and progressives say.

A generational divide, seen in newer lawmakers’ impatience with bipartisanship and for colleagues who don’t understand new media, has emerged as one of the deepest rifts within the party.