The battle for working-class voters has begun and could well determine the outcome of the 2024 elections.

Last week, President Biden and former President Trump rushed to Michigan, where the United Auto Workers have gone on strike amid contract negotiations with GM, Ford and Stellantis, the company formerly known as Chrysler.

Biden joined striking workers on a picket line outside a GM parts factory, the first time a sitting president has so thoroughly expressed support for organized labor.

You saved the auto industry in 2008, he told UAW members through a megaphone. But now they are doing incredibly well. It’s time for them to stand up for us.

Trump has not visited striking workers or endorsed the UAW’s demands for higher wages. He gave a speech at a non-union factory and accused Biden of hurting auto workers by promoting electric vehicles.

America’s workers are, to put it bluntly, screwed, Trump said. You can be loyal to the American workers or you can be loyal to the environmental nuts, but you can’t really be loyal to both.

Biden obviously disagrees. He argues that clean energy industries can and should create high-wage jobs. But UAW leaders complain that most of the subsidies from Biden’s energy law have flowed to non-union plants, and that they have not supported the president for re-election.

The battle for the hearts of autoworkers is a microcosm of a larger struggle for working-class voters, a category typically defined by pollsters as voters without a college degree. They make up about 60% of the electorate.

Working-class voters, especially union members and their families, were once the cornerstone of the Democratic Party. But over the past half century, as Democrats became more liberal, millions of white, non-college-educated voters moved toward the Republican Party and its conservative social policies, a phenomenon political scientists call class inversion.

Did you ever think we would find ourselves in a situation where workers would vote Republican? the president worried earlier this year to members of the Democratic National Committee. Many of them came to believe that we were no longer paying attention [the] working class as we used to do.

In 2016, Trump won the presidency in part by winning over nearly two-thirds of white non-college voters, a key reason why he prevailed in former Democratic strongholds such as Michigan, Wisconsin and Pennsylvania. Democratic candidate Hillary Clinton won only 28% of those voters.

In 2020, Trump won 65% of the white working-class vote, but Biden improved on Clinton’s dismal performance by winning 33%, according to a Pew Research Center survey. That was enough to move Michigan, Wisconsin and Pennsylvania into the Democratic column.

So Biden doesn’t need to win a majority of non-college-educated voters to keep his job in 2024, he just needs to do about as well as he did in 2020.

Above all, he must maintain support among union members and their families, most of whom still vote Democratic. In 2020, Biden carried union households in Michigan by a whopping 25 percentage point margin, from 62% to 37%.

That’s why Biden so often reminds the public that he considers himself the most pro-union president in American history.

Trump doesn’t make that claim. In his four years as president, he implemented a traditional pro-business Republican agenda and appointed anti-union members to the National Labor Relations Board.

His appeal to working-class voters in Michigan last week was a reiteration of the themes he addressed in 2016 and 2020, both cultural and economic.

I risked everything to defend the working class against the corrupt political class, he claimed.

He pledged to undo Biden’s clean energy mandates, promote oil and gas drilling and impose high tariffs on foreign goods, all of which he said would be good for auto workers.

Biden, despite all his history as a supporter of organized labor, has a tougher case to make.

After two years of high inflation, most voters feel they are worse off financially than under Trump. And they’re right: Census Bureau estimates suggest that real household income, which began falling in 2020, has not yet returned to its pre-pandemic peak.

Biden’s response has been a series of economic stimulus, investments in infrastructure and clean energy, and policies to promote higher wages, a package he has dubbed Bidenomics.

But even as real wages have risen faster than prices in recent months, most working families say they still don’t feel better off.

Bidenomics is based on the hope that by this time next year, most Americans will find their paychecks rising faster than their grocery bills, and the president will take credit for this.

But some Democrats are concerned.

The term Bidenomics seems perfectly designed to irritate voters rather than win them over, says Ruy Teixeira, a centrist Democratic political scientist.

It would be better, he suggested, for Biden to focus his pitch on the ways he is pushing companies to raise wages, including federal regulations requiring overtime for more workers.

Regardless, unless the economy begins to improve more dramatically, the 2024 election will likely remain close. And the nominees of both parties, whoever they turn out to be, will spend much more time speaking to workers in Michigan, Wisconsin and Pennsylvania.