The outspoken group of Democratic-leaning voters on social media is outnumbered, roughly 2 to 1, by the more moderate, more diverse and less educated group of Democrats who typically don’t post political content online, according to data from the Hidden Tribes Project. This latter group has the numbers to decide the Democratic presidential nomination in favor of a relatively moderate establishment favorite, as it has often done in the past.
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The relative moderation of Democrats who are not sharing their political thoughts on social media, and therefore of Democrats as a whole, makes it less surprising that Virginia Democrats tolerated Mr. Northam’s yearbook page. It makes it easier to imagine how Joe Biden might not merely survive questions about whether he touched women in ways that made them feel uncomfortable, but might even emerge essentially unscathed.

It also helps explain why recent polls show that a majority of Democrats would rather see the party become more moderate than move leftward, even as progressives for a Green New Deal or Medicare for all.
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The Hidden Tribes Project, conducted by More in Common, is a nonpartisan representative YouGov survey of 8,000 Americans that divided respondents into different groups, or “tribes,” based on their responses to dozens of questions. The characteristics of these groups help make sense of the different ways Democrats have run and won primary elections.

In reality, the Democratic electorate is both ideologically and demographically diverse. Over all, around half of Democratic-leaning voters consider themselves “moderate” or “conservative,” not liberal. Around 40 percent are not white.