The numbers tell the story: Clinton has won more pledged delegates than Sanders. She’s won the commitments of more superdelegates than he has. (More on that in a bit.) She’s won more state contests than he has.

As Nate Silver points out, Clinton won the strictly Democratic vote in all but three primaries and caucuses, while Sanders won the independents in all but three. In other words, Democrats have already coalesced around Clinton. One of Sanders’s great accomplishments has been bringing those non-party members into the process. How many of them will back Clinton in a general election? Their support could be the difference between a comfortable cruise over Donald Trump and a nailbiter or loss on November 8. The numbers have varied a little bit, and as the last stretch of the primaries neared, Clinton’s negatives soared with Sanders backers. Polls have shown perhaps a quarter of Sanders voters saying they won’t back Clinton. (A recent MTV poll found that only 57 percent of Millennial Sanders backers would pull the lever for her, though.) Most Democrats also feel the primary process was fair.

But as Philip Bump has shown, more Clinton voters were threatening to vote for John McCain in 2008 than Sanders supporters are threatening to defect to Trump this time around. Past experience suggests that after acrimonious primaries, likeminded voters generally come back together. This year could be an outlier, but the track record warns against assuming it is. Clinton also benefits from running against Donald Trump, who is generally unpalatable to the people who back Sanders—despite the various anecdotal suggestions that there’s a sizable Sanders-Trump constituency.

The Sanders campaign’s case for continuing on is a two-part argument. The first is that those superdelegates aren’t bound by their commitments to Clinton so far, and they could change their mind before the Democratic National Convention in July. The second is that Sanders will appeal to those superdelegates to abandon Clinton, on the basis that head-to-head polls show him performing better against Trump than Clinton does.

There was a time when those head-to-head polls could be easily dismissed as too early. That’s less true now. But given that Clinton still leads Trump, the electability argument is less compelling. It’s also somewhat un-democratic. Sanders wants to convince superdelegates that they should circumvent the desires of the majority of Democratic voters across the country and hand the nomination to him. (I'm old enough to remember when Sanders thought that superdelegates were “problematic” and should vote according to the preferences of their home states. Strangely, now that Clinton has won more states, he’s not making that case.) You may recall this as the same argument that Republicans like Ted Cruz and John Kasich were making ahead of Donald Trump winning the nomination: They argued that even though Trump had won far more votes, Republican delegates should give one of them the nomination because Trump couldn’t win a general election. We know how that turned out. Republican voters roundly rejected that as un-democratic, and Trump quickly cleared the field.