SAN DIEGO — Bernie Sanders has not left the building. And —even after losing three more states this week (Florida, Arizona and Illinois) — he stubbornly refuses to leave the stage. Even with no discernible path to victory, the renegade Vermont senator won't quit the race for the Democratic presidential nomination.

Sanders' aides say that he plans to stick it out at least until April 28 — otherwise known as an eternity from now — when voters in New York and other states go to the polls.

If that will even be happening at that point. Ohio Gov. Mike DeWine this week closed the polls in the Buckeye State because of fears about spreading the coronavirus. Next month, other governors might do the same.

Sanders' last debate performance — which was surreally delivered without a live audience — did not inspire confidence that he's up to the task of keeping millions of Americans safe and healthy. That's hard to do when you threaten to turn the nation's existing health care system upside down in the midst of a pandemic, or when you confuse the coronavirus with the Ebola virus.

Be that as it may, right now Sanders isn't going anywhere. He is having too much fun tweaking the Democratic establishment. During the debate, Sanders didn't pull punches against the presumptive nominee.

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One thing we're starting to hear from the media is that — while Sanders is not destined to win the nomination — he did succeed in raising the right issues.

Is that so? Well, I can think of at least one especially thorny issue that Sanders has avoided like, well, the coronavirus. It's an issue that grew out of the immigration debate, and it threatens to tear apart the Democratic coalition.

An underreported facet of the immigration debate is the constant friction between working-class whites and Latino immigrants. Many in the former group want fewer foreign workers because they fear competition, and they're convinced that immigrants will work for lower wages. Meanwhile, the latter group wants more foreign workers, because they recognize that many jobs won't get done without them and think hard work ought to be rewarded.

And guess who finds himself smack dab in the middle? Bernie Sanders.

Even having this discussion causes severe heartburn for Democrats. That explains why so many of them — including Sanders — would just as soon gloss over it. Sanders isn't able to do that, however, because he has stuck his neck out and aggressively pandered to both sides of the debate. And no politician wants to referee a fight between rival tribes of supporters.

Sanders must explain to his fellow Americans how he went from hardline Nativist Bernie to the person Rep. Alexandria Ocasio-Cortez, D-N.Y., calls "Tío Bernie."

For most of his 40 years in politics, Sanders has been a protectionist — not just when it comes to trade but also when it comes to the labor force. He has warned time and again that immigrants take jobs from Americans and drive down wages for U.S. workers. He said it loud, and he said it proud — to fellow nativists like Lou Dobbs. In 2007, the then-CNN host brought Sanders onto his show and let the senator brag about helping to kill the guest worker provisions in a once-in-a-generation comprehensive immigration reform bill, a move that ensured the demise of the legislation.

But now that Sanders is holding on to his presidential bid by his fingertips, the senator is singing a different tune. The new music is due to the fact that most of his primary victories — including California, Colorado, Nevada and Utah — are due to support from Latino voters who appreciate his efforts to reach out to them. The new, kinder and gentler version of Sanders talks about the contributions of immigrants and promises, if elected president, to do in the first 100 days what he has refused to support over the last four decades: legalize the undocumented.

During last Sunday's debate, Biden called Sanders on the contradiction, and Sanders tried to slip out of it by presenting his past legislative shenanigans as being fueled by his concern that guest workers would be treated like slave labor — a concern he neglected to mention to Dobbs.

Sanders is as slippery as they come. He's a first-rate con man who divides people, plays to all sides, and will say anything rather than own up to his mistakes.

That sounds familiar. It's almost a shame we won't get the chance to see him square off this fall against his alter ego — President Trump.

Ruben Navarrette can be reached at