GRAND RAPIDS, Mich. — Vice President Kamala Harris rallies in Michigan’s union halls, standing alongside the state’s most powerful labor leader, while former President Donald Trump fires back from rural steel factories, urging middle-class workers to trust him as the true champion of their interests.

As they compete for blue wall states with deep union roots, the presidential candidates are making their case to workers in starkly different terms.

And nowhere is that contrast more significant than in Michigan, where both candidates are vying for workers’ support in a race that could mark a pivotal moment for organized labor.

“The American dream was really born here in Michigan,” United Auto Workers President Shawn Fain told a crowd of several hundred while campaigning for Harris in Grand Rapids. Fain, who described Michigan as “sacred ground” for his union at the early October rally, warned that the dream was on “life support” and that unions like his were key to protecting it for American workers.

Harris, who is planning to meet with union workers again in Michigan on Friday, hopes her message — amplified by supporters such as Fain — will resonate beyond the union families that once formed a rock-solid base for the Democratic Party. Her campaign has grown increasingly concerned about her standing with men in the blue wall states of Michigan, Wisconsin and Pennsylvania, where they are looking to union leaders to help mobilize voters in a political landscape that has shifted in the winds of a rapidly changing economy.

These concerns intensified recently when Harris failed to secure two key union endorsements that in 2020 went to President Joe Biden, who has touted himself as the most labor-friendly president in U.S. history. The International Association of Firefighters and the International Brotherhood of Teamsters both declined to endorse anyone, with the Teamsters citing a lack of majority support for Harris among their million-plus members.

The Teamsters have traditionally been less reliably Democratic than other unions, having endorsed Republican Presidents Richard Nixon and Ronald Reagan in the past. Some state-level unions have also diverged from their national leadership, with Michigan’s Teamsters and California’s main firefighters’ union backing Harris.

Trump has seized on the union non-endorsements, claiming they prove rank-and-file workers support his vision for the country.

Many Midwestern communities once core to the labor movement have shifted to the right in recent decades, often in response to economic concerns such as deindustrialization and the removal of trade barriers. In that same span, non-college-educated white voters across the country began voting more conservatively for a number of reasons, including concern about cultural issues involving race and gender.

In Michigan, home to the Big Three automakers and the largest concentration of UAW workers, Trump seeks to capture an even larger share of these votes by framing Harris as a supporter of electric vehicle mandates and trade policies that he says send jobs overseas.

Attempting to separate union workers from their leaders, he labeled Fain a “stupid idiot” and praised Tesla CEO Elon Musk for firing workers who went on strike. The UAW says that could intimidate people who work for the Trump campaign or at Tesla who might want to join a union.

In 2020, Biden narrowly carried the blue wall states that had broken with Democrats in 2016 for the first time in decades on his way to winning the White House. That election win was built on a foundation of strong support from unionized voters, who have traditionally formed a turnout machine for Democrats in the Midwest. But it stood apart from past Democratic victories in a number of significant ways.

While Trump narrowly won white voters in Michigan in 2020, the former president’s vote margin was highly polarized along educational, professional and income lines; Trump won nearly two-thirds of non-college-educated white voters in the state, while Biden and Trump were drawn to a near tie among college-educated white voters, according to AP VoteCast, a comprehensive survey of the electorate.

But with the 2024 presidential season pushing into its final weeks, Harris and Trump are also scrambling to win votes in key constituencies outside of unions.

A coalition of Republicans backing Harris, including former Illinois Rep. Adam Kinzinger, campaigned with her in pivotal Pennsylvania before she sat down with Fox News for an interview that aired Wednesday evening.

GOP nominee Trump, meanwhile, appeared on TV Wednesday in two town halls — one with a woman-only audience that Fox News Channel recorded Tuesday, and the other with Hispanic voters, hosted by Univision, the nation’s largest Spanish-language television network.

Trump has been counting on increased support among Latino voters even as he centers his campaign on a sinister view of immigration, suggesting migrants are “poisoning the blood” of the nation.