Democrats won South Carolina’s First, which stretches from the posh coastal towns of Hilton Head and Beaufort to the Charleston suburbs. The district was formerly held by the very conservative Mark Sanford. Trump won it by 13 points in 2016; freshman Representative Joe Cunningham nabbed it by only one point in 2018.

Democrats won New York’s Twenty-Second, which extends from the university city of Binghamton to postindustrial Utica. Trump won there by a staggering 15 points in 2016; Anthony Brindisi defeated by two points a Republican incumbent prone to incendiary comments like—in a radio interview shortly after the Parkland school shooting—“It's interesting that so many of [the] people that commit the mass murders end up being Democrats.”

Altogether, 31 of the congressional districts won by Trump in 2016 are now held by Democrats, 21 of them freshman. Only three Hillary-won House districts are represented by Republicans.

Democrats succeeded in Trump country because the Democratic Party attracted a broad coalition of moderates and liberals. The Sanders campaign aims first and foremost to reinvent the Democratic coalition as a narrower ideological movement, in much the same way that the once-broad Republican coalition has been transformed. But the difference between the two is that many fewer Americans identify as “progressive” than as “conservative.” Worse for Democrats: Not only does Sanders propose to break the cookie in such a way as to leave his party with the smaller piece, but he also does so in a political context that already disfavors them.

Democrats hold virtually every one of the urban and academic districts that will rally to progressive politics. But thanks to enterprising candidates who keep in touch with their districts, they also hold Minnesota’s Seventh, a 90 percent white district running north-south adjacent to the two Dakotas. It’s represented in Congress by Collin Peterson, a pro-life Democrat who chairs the House Agriculture Committee. In 2018, a Democrat won the country’s richest congressional district, the Virginia Tenth, which has a median household income of more than $127,000. Democrats now represent all of the country’s 10 richest districts.

Peter Beinart: Regular Democrats just aren’t worried about Bernie

Sanders supporters take as an article of faith that Sanders will win votes from working-class voters who swung to Trump in 2016. This idea is based on a single data-point: Some 10 to 12 percent of those who voted for Sanders in the 2016 primary then voted for Trump in the general election. If Sanders could have held all those primary voters in a general election, and also if he had won everybody who voted for Hillary Clinton in the primary, then he would have defeated Trump. But once you state the two ifs, you see the problem.

The political scientist Brian Schaffner, who closely studied these Sanders-Trump switchers, finds that they were older white voters with conservative racial views. As compared with other Sanders voters, the Sanders-Trump switchers were much more likely to deny that white people enjoy special advantages in American society. They were also much less positive about President Obama than were Sanders voters who did not switch to Trump.

But there does appear to be a racial component to this, as defectors are much more likely to disagree that whites are advantaged in US 9/n pic.twitter.com/zcoHm9APNf — Brian Schaffner (@b_schaffner) August 23, 2017

No Democrat, including Sanders, is likely to outbid Trump for these voters in a general election.