Matt Damon went deep into red state identity politics to build his character in Tom McCarthy’s Cannes premiere “Stillwater.”

To portray Oklahoma oil rig worker Bill Baker — a father who sacrifices everything to help free his daughter from a French prison, after she is convicted of murdering her roommate while studying abroad —— Damon spent an “absolutely critical” time doing research in the state, he said at a Friday press conference for the film.

One of the biggest laughs at the movie’s Thursday night premiere came when Damon’s character is asked by a French woman if he voted for Donald Trump. He did not, he responds, but only because a prior felony kept him from voting at all.

On Friday, Damon said Baker absolutely would’ve supported Trump.

“These guys don’t apologize for who they are,” Damon said, referring affectionately to his character as a “roughneck.” The actor and his director McCarthy road tripped through Oklahoma prior to shooting, where they were invited into the break rooms and backyard barbecues of the real men who inspired the character.

“They’re in the oil business, of course he voted for Trump,” Damon said. “These people were wonderful to us, they really helped us. It was eye-opening for me.”

The actor said he came to appreciate the smallest details — from wearing a specific kind of blue jeans treated with fire retardant, which “changes the way these guys walk,” Damon said. “They all have goatees, the sunglasses. They’re not six-pack ab guys, but they’re strong. You go to their barbecues and a guitar comes out and they start singing Church songs.”

Damon, an outspoken Democrat, had been critical of Trump throughout his presidency. In 2017, Damon called the former president’s response to Charlottesville “absolutely abhorrent.”

Reviews of “Stillwater” emphasized how expertly the film shows how the world feels about America right now. McCarthy didn’t disagree, but also said it boils down “to relationships, and how we connect to each other.”

Damon stars with Camille Cottin, Abigail Breslin, and Lilou Siauvaud. The Focus Features film opens in theaters on July 30 in the United States .