“I’ve never seen anybody mount a comeback like this — ever,” Matt Seyfang, an expert delegate counter who had worked for Pete Buttigieg, said of Biden’s unexpected rout…

The scale of his win was big geographically — running from the Chesapeake Bay in Virginia to the West Texas plains — as well as demographically. Biden won black voters by huge margins, but also got more support from women than the only woman in the race. He scored in the suburbs and rural areas of the South and West. His major weaknesses were with young people and Latinos, with whom Sanders mopped up in California, Colorado and parts of Texas…

With no ad budget to speak of and a shoestring organization, Biden put on a three-day exhibition of how to leverage pure momentum into a massive victory. He also showed that his abysmal showings in predominantly white Iowa and New Hampshire didn’t matter that much, after all.

“In Democratic presidential primaries, some candidates underestimate the importance of African-American and older voters,” said Steve Ayscue, a Democratic strategist. “Conventional political wisdom isn’t always right. But this has been pretty consistent.”