Mayor Bill de Blasio, who backed Hillary Clinton through most of the presidential race, said yesterday that Vermont Sen. Bernie Sanders was the candidate with the message that “would have won the election”—though he professed uncertainty about what a race between Sanders and Donald Trump would have looked like.

In the weeks ahead of the election, the liberal Democratic mayor claimed that his belated endorsement of Clinton pushed her to adopt a more left-wing posture, and a platform that he called “most progressive of any Democratic nominee in many decades.” In the immediate aftermath of the election, however, he insisted that her platform lacked progressive populist economic message.

“Everyone asks that question and the first thing to say is it’s highly theoretical, right,” de Blasio told ABC7’s Bill Ritter on Sunday. “We don’t know how all the facts would have played out. I think Bernie would have had some real strengths but also some real weaknesses. I think the message would have won the election, the message would have won the election.”

The mayor said that his former boss had the same message in her campaign platform but that she downplayed it in the last few months of the election, including the debates—a time at which he said Clinton “should have been pumping it up.” This, de Blasoi argued, cost her states like Wisconsin and Pennsylvania that traditionally vote on the Democratic Party line.

“I say it with tremendous respect for her and again, she won 2.6 million more votes than Donald Trump so it’s kind of hard to ignore that fact,” de Blasio continued. “But I believe if she had had a message of economic change, it would have overwhelmed a lot of what Trump was putting forward, I think it would have helped her to keep some of those states.”

Trump “wisely ran” an outsider, challenging both the Republican and Democratic leadership, de Blasio said, calling it a “very brilliant move on his part.” But he warned that voters could be in for disappointment if Trump does not follow through on his promises.

“I think those people in the heartland want to see different results but I would argue a lot of them depend on federal investment too to be able to have hopes economically and that also could become a contradiction if they don’t get help they deserve,” he said.

De Blasio also weighed in on his criticism of Trump on Twitter after the president-elect tweeted that Chuck Jones, president of United Steelworkers 1999 “has done a terrible job representing workers” after Jones accused him of lying to workers at the Carrier plant in Indiana. Trump had claimed online days earlier that he had convinced the air conditioner company to keep 1,100 in the United States.

The actual tally was hundreds fewer.

Sorry @realDonaldTrump. Unions like the Steelworkers, leaders like Chuck Jones are going to save this country from your anti-worker policies https://t.co/psQI31geNf — Bill de Blasio (@BilldeBlasio) December 8, 2016

On TV, de Blasio argued Jones was merely stating that the union stood up for the workers by bringing attention to the fact that the jobs were going to Mexico—that this forced the Indiana government to start paying attention and that “Trump came in later.”

“If the workers and if Chuck Jones had not stood up and said, ‘Wait a minute, you’re not taking our jobs away,’ this never would have been this wonderful photo-op for Donald Trump,” de Blasio said.

Organized labor has gotten a “really raw deal” in the United States in the last few decades, the mayor said.

“I worried about a lot of the free market instincts of Trump and what it’s gonna mean for the labor movement,” de Blasio said. “I think a lot of Republicans are licking their chops, hoping they can repeal a lot of labor law at this point. And I think it’s important to lay down the marker early that there’s gonna be a fight over that.”