At the same time, he brings to the contest three major strengths that would be important in the general election.

First, he gets strong backing from young voters. A late March Quinnipiac survey found, for example, that Sanders won 26 percent among Democrats under the age of 45 and 16 percent among those over 45. One of Hillary Clinton’s weaknesses in 2016 was a failure to turn out young, Democratic-leaning voters.

The second Sanders asset is the exceptionally high levels of support he receives from small donors who contribute $200 or less. In this election cycle, Sanders has not only raised more than any of his competitors, at $18.2 million, but a higher percentage of his receipts, 84 percent, has come in amounts under $200.

A third advantage Sanders brings is the appeal of his anti-corporate, anti-rich message to a segment of populist Trump voters — those who backed Sanders in the 2016 primaries and shifted to Trump in the general election.