BOSTON (CBS) – On March 11, the date the NBA suspended the season due to the coronavirus outbreak, Joe Biden led President Trump by seven points in the Real Clear Politics polling average.

Now he leads by eight.

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As we head into Thursday night’s final debate (watch it on WBZ-TV and CBSN Boston at 9 p.m., then join us at 11 p.m. for highlights and my analysis) a common theme is that it represents a final chance for Trump to “shakeup the race,” “pivot,” “change the narrative” – take your pick.

And I suppose it is within the broadest conceivable realm of possibility that Biden could forget to wear makeup and sweat profusely (Nixon 1960), promise to raise everyone’s taxes (Mondale 1984), react to a scenario of his wife being raped and murdered by bloodlessly denouncing the death penalty (Dukakis 1988), compare himself with John F. Kennedy (Quayle 1988), or look bored and check his watch (George H.W. Bush 1992).

But I’m guessing none of that will happen.

The former vice president will never make anyone forget Demosthenes. But Google “Biden’s latest gaffe” and the worst you get is a September reference to the “Harris/Biden ticket,” unlikely to be a deal-breaker.

It’s also possible, in theory, that Trump will tonight display a complete personality transformation, shedding his scatter-shot bluster, random insults of popular public figures like Dr. Fauci, grotesque slanders of Biden and his family and farcical downplaying of the pandemic, instead coming across as a combination of FDR, Ronald Reagan, Sir Laurence Olivier and Sean Connery as Bond.

But don’t hold your breath.

And unless one or both of those extremely unlikely scenarios unfold, this debate, while well worth watching, will be meaningless. The cake is baked, and it might not even need frosting.

There’s no doubt the pandemic and his handling of it has hurt Trump’s re-election chances. You can see the damage in battleground state polls where comfortable Trump leads last winter have evaporated, and previously out-of-reach red states are now competitive. It’s shocking, really, because all Trump ever had to do was come before the cameras, express concern and empathy, and turn the mic over to Fauci and company.

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But the fact that Biden held the same lead nationally on March 11 that he enjoys today tells you that the virus isn’t the sole reason for Trump’s electoral woes.

Two things happened, one that took three years, the other just a few days.

The astonishing reincarnation of Biden from sad Democratic also-ran, bailing on New Hampshire primary night ahead of an embarrassing defeat, to triumphant Super Tuesday champ three weeks later, was a crucial moment. Do you really think Bernie Sanders would be doing better than Biden right now?

But long before the Democrats put their house in order, Trump was busy trashing his. His litany of unforced errors, from the chaotic bungling of the early 2017 travel ban to the Tasmanian Devil act at the first debate last month, erected and cemented historically-poor approval ratings and a likely-fatal gender gap.

I’ll never forget the lunch hour I spent at a diner in Billerica – one of the few Massachusetts communities Trump won in 2016 – sampling voter opinion on his first 100 days in office. Asked what they liked about the new president, Trump supporters offered a variety of responses, but they were unanimous about what they didn’t like – the tweeting.

Talk about unforced errors.

So, what to expect from this final debate? More of the same from Trump: undisciplined anger and self-pity, patently false claims, laughably narcissistic self-praise.

His people say the president’s being coached to talk less, thus leaving more time for Biden to somehow expose himself as an incoherent fool.

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Funny thing. That’s been the Biden strategy all along.

Jon Keller