The dueling appearance at the International Association of Firefighters Convention, confirmed by a source familiar with Vance’s schedule, comes as both parties battle for working-class votes.

Walz spent the bulk of his remarks Wednesday focused on Vice President Kamala Harris’s support for pro-labor legislation and his own career as a public school teacher.

“I can promise you this: When Vice President Harris and I win this election, we’ll have your back just like you’ve had ours this entire time,” Walz told members.

The union event was the second Walz has attended. Two weeks ago, he spoke at a conference of municipal workers in Los Angeles, his first solo speech as Harris’s running mate.

Meanwhile, Vance spent Wednesday speaking to truckers in Eerie, a swing county in Pennsylvania. He grabbed headlines for telling Harris to “go to hell” over the Biden administration’s botched withdrawal from Afghanistan.

Walz was chosen by Harris, in part, for his perceived ability to speak to blue-collar workers. He caught the eye of labor leaders for his pro-union record as governor of Minnesota.

But former President Donald Trump is betting he, too, can use his running mate to appeal to the working-class vote. Vance frequently talks about his Rust Belt upbringing, captured in his best-selling memoir Hillbilly Elegy.

Vance will be introduced by Rep. Carlos Gimenez (R-FL), a former firefighter, at Thursday’s union event.