Sanders’ white working class problem was well-described by Nate Cohn in a recent article:

“Mr. Sanders has so far failed to match his 2016 strength across the white, working-class North this year, and that suggests it will be hard for him to win Michigan.

This pattern has held without exception this primary season. It was true in Iowa and New Hampshire against Pete Buttigieg and Amy Klobuchar. It was true in Maine, Minnesota, Massachusetts and even Vermont on Super Tuesday against Mr. Biden.

Over all, Mr. Biden defeated Mr. Sanders by 10 points, 38 percent to 28 percent, in counties across Maine, Minnesota and Massachusetts where white voters made up at least 80 percent of the electorate and where college graduates represented less than 40 percent of the electorate. According to the exit polls, Mr. Biden was tied or ahead among white voters in every state east of the Mississippi River on Super Tuesday.

This is a marked departure from 2016. Back then, Mr. Sanders tended to excel among white, working-class and rural voters across the North. This made Michigan, where white voters represent a well-above-average share of the Democratic electorate, one of his stronger states. He dominated in Michigan’s small towns and rural areas, losing only in few counties that tended to have older voters….

Mr. Sanders has often made up for losses in white, working-class areas this year with gains among Latino voters and white voters who live in left-liberal areas. In a sense, he has traded strength in states like Maine and Minnesota for strength in California. This is a bad trade in Michigan, where Latino voters make up only a sliver of the Democratic electorate. It may be an even worse trade in Michigan than it was in Minnesota or Maine, since there are relatively few overwhelmingly Democratic left-liberal enclaves akin to Minneapolis or Portland, Maine. Only Ann Arbor and Lansing fall into a similar category.”

This does not sound promising–at all–for Sanders.