WASHINGTON — Even a presidential candidate’s most devoted supporters could be forgiven for trying to tune out the torrent of campaign emails, Twitter messages, Facebook posts, Instagrams and Snapchats that steadily flood voters’ inboxes and social-media feeds in this digitized, pixelated, endlessly streaming election cycle.

But a text message is different.

A text message — despite its no-frills, retro essence — is something personal. Something invasive. Something almost guaranteed to be read.

So last month, when Senator Bernie Sanders of Vermont staged what his aides called the most important night of his three-month-old campaign for the Democratic nomination — cramming 100,000 of his followers into house parties from coast to coast, to whip them into foot soldiers — he did not solicit email addresses or corral the attendees into a special Facebook group. Instead, his digital organizing director, Claire Sandberg, asked each participant to send a quick text establishing contact with the campaign.

“We need to turn crowds and popular support and Bernie into winning,” she said over a video hookup. “So everyone, please, take out your smartphone right now and text the word ‘work.’ ”