(Matt McClain/ The Washington Post)

Here's a telling exchange between MSNBC's Andrea Mitchell and Jeff Weaver, manager of Bernie Sanders's campaign, on Tuesday afternoon:

Mitchell: "Have you flipped any superdelegates yet?

Weaver: "No."

The entirety of Sanders's remaining chances in this race — such as they are — rest on persuading large numbers of superdelegates to switch from supporting Hillary Clinton to supporting him. Without such a broad-scale switcheroo, Sanders loses. Because of math.

This is that math. Clinton has 1,812 pledged delegates and 572 superdelegates, according to NBC's calculations. Add it up and you get 2,383 — a simple majority of all available delegates. Hence, the race is over.

(Philip Bump / The Washington Post)

Unless, of course, you ascribe to Sanders's logic on superdelegates, which goes like this: They are unbound until the actual vote at the Democratic National Convention in July. Therefore, who they say they are for today is entirely immaterial.

Which is technically correct but, as proven by Weaver's admission that Sanders has swayed a total of zero superdelegates to his side, is, sort of, besides the point. We are not talking about persuading five or 10 or even 50 superdelegates to change their minds. Clinton is at 2,383 before the six states' votes are counted, including the massive delegate treasure trove of California. She will be well above that number by the time all the delegates from today's primaries are allocated.

What Sanders needs to do, then, is not only to find an argument that convinces superdelegates that they should switch their support to him — which he has not yet done even one time — but also to do it on a grand scale.

It's at this point that you have to ask yourself how Sanders could do that — short of a Clinton indictment in the ongoing FBI investigation into her private email server during her tenure at the State Department. Simply put: It's very hard to imagine.

Sanders argues that many of the superdelegates for Clinton pledged to support her before he was even in the race and they knew they had an alternative. Two things wrong with that argument: 1) Why, then, has Sanders not been able to persuade a single one of those people to flip to him? 2) Why would superdelegates — no matter why they were for Clinton at the start — change their minds now? Clinton has won the most pledged delegates. She has won the most raw votes. In fact, there's not a single measurement of support in the Democratic race in which Clinton isn't ahead of Sanders. Nothing that happens today in California or anywhere else will change those facts.

To argue that Sanders still has a real chance in the Democratic race is to assume that everything that has happened this year — up until this exact minute — tells us absolutely nothing about what will happen tomorrow and every day between then and the start of the Democratic National Convention. That superdelegates, none of whom have moved to Sanders yet, will do so in droves suddenly.

Is it possible? Sure, in the sense that anything that hasn't already happened can't be totally ruled out as a possibility.  But, short of a lightning strike — times 200 or so — Sanders's promise to persuade large numbers of superdelegates to be for him just isn't going to happen.