At a morning meeting last month, Sonic executives were discussing a new marketing strategy. In a show of how successful its two-men-in-a-car commercials have been — TV ad spending is the company’s biggest marketing expense — they were hoping to replicate that formula with two women. (Company executives frequently mention that 58 percent of the Sonic’s customers are women.) Names of female comedians and actresses were being tossed out. Among the hoped-for criteria projected on the room’s wall was a note to avoid political choices.

Sonic is rare for the number of women and minorities in its top ranks, including its chief financial officer, chief marketing officer, chief brand officer and general counsel. And as of this month, white males are a minority of the independent directors on its board; including Mr. Hudson, they account for half of the group. (To put that in perspective, recent data from Equilar shows that women account for only 16.5 percent of the board members of Russell 3000 companies as of Dec. 31.)

Ms. Thronson, who was previously the senior vice president for global marketing at Marriott, said that it was new for her to serve on a board with four women but that the change didn’t take place overnight: “It’s not investors and outside people saying, ‘Do this,’ but really believing there is something about cognitive variety and that different perspectives create better outcomes.”

As for how it influences boardroom dynamics, she said, “When there’s one, we’re a token, and by four, it takes gender off the table.”

Mr. Hudson started at Sonic’s legal department in the 1980s after attending law school at Georgetown University. He became its chief executive in the mid-1990s after helping take the company public. In that time, the company and society have continually changed.

“There’s a lot of folks that feel like the America they understood in the ’50s, ’60s and maybe the early ’70s is an America they don’t understand today as much, and they’re reacting to that,” Mr. Hudson said. “But this is where leaders of all sorts can talk about a big tent instead of talking about a divisiveness, and talk about how we approach this so we have opportunity for everybody instead of a divide-and-conquer approach.

“The strongest thing we can do,” he added, “is attempt to lead by example and be open about it.”