If Raphael Warnock wins today’s Senate runoff in Georgia, Senate Democrats will gain a 51-49 majority – providing them with some insurance if Arizona voters boot out Kyrsten Sinema in 2024, while at the same time reducing the power of the West Virginia Democrat Joe Manchin to control the Democrat’s agenda.

In other words: a win-win.

But it could prove an even bigger Democratic win. That’s because the biggest loser in a Warnock victory won’t be his Republican rival, Herschel Walker.

It will be Donald Trump.

Walker’s entire candidacy was a Trump creation – not unlike Trump University, Trump Airline, Trump Vodka and Trump Steaks.

And like those businesses, the Walker candidacy appears to have sunk under a miasma of ineptitude, lies and embarrassing allegations – in this case, of domestic abuse, semi-secret children and payments for abortions for multiple women.

Trump encouraged Walker to run. Before Walker announced his campaign, Trump loudly hinted that the former NFL star was considering entering the race. Earlier this year, Trump went to Georgia to stump for him.

But after the 2022 midterms, when so many Trump-endorsed candidates flamed out, Walker’s campaign asked Trump to please stay away. No more endorsements, rallies, stumps or joint appearances.

Grudgingly, Trump complied. But his corpulent shadow has continued to dog Walker’s slipshod campaign.

In many respects, Georgia is becoming Trump’s Waterloo.

Earlier this year, Georgia’s Republicans rejected Trump’s chosen primary challengers to Governor Brian Kemp and Secretary of State Brad Raffensperger.

In a typical display of distemper, Trump targeted both for defeat after they refused to help him subvert the presidential election results in 2020.

Recall that Trump had urged Kemp to support efforts aimed at decertifying his loss, and had threatened and pleaded with Raffensperger to “find 11,780 votes, which is one more than we have”.

These efforts are now the subject of a criminal lawsuit against Trump in Georgia.

If Georgia is a bellwether for American politics, it has been pointing in a direction opposite Trump.

In 2020, after enduring four years of Trump’s presidency, Georgians voted for a Democrat for president for the first time in 28 years, and also elected both Warnock and Democrat Jon Ossoff to the Senate.

Trump’s endorsement has become such a kiss of death in Georgia that Warnock’s campaign ran ads consisting entirely of Trump praising Walker, along with the words “Stop Donald Trump” and “Stop Herschel Walker”.

Georgia isn’t quite a microcosm of America. It’s more likely a microcosm of the future of America.

Since 2000, the state’s population has surged, particularly among young people and people of color. The foreign-born population now exceeds 10% of the state’s total.

Atlanta has become a hub of youthful innovation and knowledge work, including upwardly mobile Black professionals.

Warnock and Walker are two Black men in a runoff contest created decades ago to thwart Black candidates. Georgia has never had two Black nominees compete for the Senate.

Affirming Georgia’s status as a political keystone, the Democratic National Committee’s rules committee last Friday took a step toward making Georgia an early primary state.

Across America, red states are gaining purple hues. Their more urban and educated precincts have become wealthier – and Democratic – while their white rural hinterlands remain economically stagnant, and Trump Republican.

The same trend is apparent even in heavily Democratic states like California and New York, where economic and demographic changes are producing wealthier, more educated and diverse urban regions surrounded by outlying regions populated by an ever more precarious white working class – Trump’s base.

The Trump base is no longer large enough to swing elections in Georgia or other key states. But it is big enough to destabilize America because of its continued receptiveness to Trump’s conspiracy theories and “big lie”.

Trump’s growing desperation makes this an incendiary combination.

His 2020 loss, the rejection of his candidates in the 2022 midterms, and the mounting lawsuits against him have made him even more intent on being the center of the nation’s attention, fueling his base’s paranoia, and winning, somehow.

Three weeks ago, he delivered a lie-infested announcement that he was running again for the presidency.

Two weeks ago, he openly dined with two infamous antisemites.

On Saturday, he called for the constitution to be set aside because the 2020 election was stolen from him.

Each bonkers escalation ratchets up pressure on Republican lawmakers to disavow him. Each turns off more moderate Republicans and independent voters. Each makes it less likely that Trump-endorsed candidates like Herschel Walker will be voted into office.

But as these consequences play out, Trump’s desperation only increases.

Where will this end?

• Robert Reich, a former US secretary of labor, is professor of public policy at the University of California, Berkeley, and the author of Saving Capitalism: For the Many, Not the Few and The Common Good. His new book, The System: Who Rigged It, How We Fix It, is out now. He is a Guardian US columnist. His newsletter is at robertreich.substack.com