To win the Democratic nomination, Bernie Sanders needs to do substantially better with non-white voters. We’ve written about this again and again and again, noting that the campaign knows that it’s a problem that needs to be fixed.

It has not been fixed.

On Friday, Fox News released its latest national poll. Hillary Clinton leads Sanders nationally by a 56 percent to 34 percent margin. Among whites, she’s up two points. Among non-whites? Fifty-three.

That gap has been huge since June. It was smaller before Joe Biden decided not to run, since many non-white voters considered Biden their top choice. When he dropped out, that support mostly went back to Clinton.

This is not a problem in Iowa, which is 3 percent black (and where state polls look pretty similar to that white voter split above). It is not a problem in New Hampshire, where Sanders has a home-field advantage and where only about 2 percent of residents are black.

It is a problem in South Carolina, another early state. South Carolina is 28 percent black — a population that is largely Democratic. In 2008, more than half of the turnout for the party’s primary was black.

And in South Carolina, Sanders trails Clinton by 34 points. Among black voters, he trails by 71 points. He’s not totally unknown in the state, either. In November, a Monmouth University poll found that 29 percent of voters had no opinion of him — but 12 percent had no opinion of Clinton, either.

Saturday’s debate is one of the few remaining chances Sanders will have to make his case to Democrats, including the party’s substantial non-white base. So far, he hasn't had much luck peeling them away from Clinton. It’s not clear at this point what he can do that would.