California Gov. Gavin Newsom (D) told CNN he will not run for president in 2028 if former Vice President Kamala Harris enters the race.

Newsom made the comment during a fly-fishing outing in Montana with CNN’s Jake Tapper, as part of an ongoing series that was announced on Monday in which the anchor joins politicians in their favorite places to discuss their careers. Tapper pressed Newsom on the crowded Democrat field, noting he was not even the only potential candidate from California before naming Rep. Ro Khanna (D-CA) and Harris.

“I don’t know if she runs, but we’ll see,” Newsom said. When Tapper noted Harris had “called around,” the governor added, “But I wouldn’t run if she ran.”

Tapper asked him to confirm the line.

“Of course not. Why would I? I wouldn’t do that to her,” Newsom said. “I wouldn’t waste everyone’s time. Who needs that?”

Newsom argued a primary between the two Californians would only benefit the rest of the field, describing the scenario as “mutually assured destruction.”

“Electorally, it’s a gift from God for everybody else,” he said. “It services no greater good.”

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Tapper pushed back, pointing out that Harris has run for president twice while Newsom never has. The governor conceded the point but said their coalitions overlap too heavily.

“That would be the case you’d make. Pretty good one, actually,” Newsom said. “I know her base of supporters. I know her friends. The Venn diagram on that is just pure crossover.”

Newsom also said any decision would be run through his family first, calling his potential run for president a “non-starter” if he does not have the support of his four children.

The remarks come as Newsom trails Harris in early primary polling. A Harvard-Harris survey in April found 50 percent of Democrats preferred Harris as the 2028 nominee, compared to 22 percent for Newsom. Harris has said she “might” run again and told the BBC last year, “I am not done.” Neither has formally declared a candidacy.