Math — and specifically, delegate math — has not been Bernie Sanders’s friend in the Democratic presidential primary. And that remains the case — even as he showed some continued improvement Tuesday on one particular statistic: his performance with black voters.

Hillary Clinton took Ohio and Florida Tuesday night, the two largest delegate prizes in primaries scheduled this week. She later claimed victory in North Carolina and Illinois. Together, those outcomes give Clinton a more than 300-delegate lead over Sanders — not including superdelegates — making it quite difficult, if not impossible, for Sanders to catch up or surpass Clinton before the Democratic National Convention.

After winning Michigan last week, at least in part by gaining 30 percent of the black vote in that state, Sanders’s campaign hoped to match those those results in Ohio. He didn’t win, but as our Philip Bump notes, he did basically match his showing among black voters. Sanders won a full 28 percent of the Buckeye State’s black votes Tuesday night, according to CNN’s exit poll data. Unfortunately for Sanders, that increase wasn’t enough to deliver an overall victory in Ohio, as white voters voted more strongly for Clinton.

In Missouri and Illinois, 29 percent of black voters chose Sanders. Sanders also took 20 percent in Florida — not as good as in Michigan and Ohio, but better than the approximately 1 in 10 black voters he had been taking in some Southern states. North Carolina also looked more like those Southern states on Tuesday, giving Sanders 17 percent of the black vote. But it’s one of the last Southern states to vote, meaning Sanders’s future showings are perhaps likely to be more in line with Michigan and Ohio than the Deep South.

In short, Sanders’s voter coalition is clearly becoming more diverse. But that transformation appears to be happening at a point at which Clinton’s delegate lead is too far gone. The Sanders base also remains far from representative of the Democratic Party’s electorate.

Also apparent in the informed estimates that are CNN’s exit polls: After sweeping victories across the South, Clinton’s resounding leads with female voters of all races and ethnicities and voters of color continued in the Midwest on Tuesday. Those are big parts of the Democratic Party’s electorate and therefore have always been critical groups to win. Short of attracting a lot of independent or Republican voters, there simply is no other path to the nomination.

In Clinton’s speech Tuesday night, she talked about the challenges the next president will face, took on Donald Trump and focused much of her criticism on him. Clinton spoke about Americans who have been knocked down by some combination of social and economic policy, global economic trends and tragic encounters with gun violence and said that her campaign was about these people.

Sanders certainly did not concede the race Tuesday night. So there’s little reason to believe that the fight for the Democratic nomination will formally end this week or any time soon — especially if Sanders keeps winning states.

But, again, there is that little issue of the math.