WASHINGTON — When Fremont Rep. Ro Khanna agreed to be co-chair of Sen. Bernie Sanders’ 2020 presidential campaign, he had a requirement: no mud-slinging against fellow Democrats.

Khanna signed on early to Sanders’ campaign, having also backed the Vermont independent in his 2016 run against Hillary Clinton. But Khanna said part of the deal was that he wouldn’t attack other Democrats in the race. Those include at least one candidate from his home state, Sen. Kamala Harris, and probably Rep. Eric Swalwell of Dublin, who is expected to run.

“I said to Sen. Sanders ... when I accepted this position as co-chair that I would only say positive things about other Democrats running,” Khanna said. “And I wasn’t going to disparage other people, who I think are very talented, but I would stick to making the positive case for him.”

In a conversation with reporters this week in his Capitol Hill office, the second-term Democrat predicted the primary campaign would be less bitter than the 2016 contest was.

Noting that Sanders has been drawing large crowds to campaign events — several thousand showed up to see him at San Francisco’s Fort Mason last month — Khanna said the “urgency of beating Trump” will keep 2020 “less divisive than the past cycle.”

“If I were on some other team, I would say, ‘Well, we’ve got to be probably pretty nice to Sanders, because if we won the nomination, we’re going to need that base,’” Khanna said. “So I think that there’s a recognition — both on Sanders’ team that we’re going to need to build a coalition beyond just his supporters — and for other people that they’re going to need his supporters.”

Khanna acknowledged that doesn’t mean the primary campaign will “stay positive,” but said he already has detected less acrimony toward Sanders. He credited that to a variety of factors, including Sanders’ learning “lessons” from the last campaign and bringing on a more diverse staff with better infrastructure.

“I think there’s been a softening of the tone in the negativity around Sanders from leadership and people in positions of power,” Khanna said. “Partly I think that’s because they’ve seen his success. Partly that’s because he’s still drawing huge crowds and has huge support.” He acknowledged that Sanders isn’t universally supported, but added, “The anger toward him, I think, has mitigated in the party.”

Although Khanna says he won’t attack other Democrats, he is not afraid to draw policy distinctions with them. He was asked about a proposal from presidential candidate Sen. Elizabeth Warren, D-Mass., to break up big tech companies, some of which are located in Khanna’s district.

“I don’t think that’s effective, and I have a more nuanced view,” Khanna said. “I don’t want all the big tech companies to be Chinese, because you’re not going to break up Alibaba, Baidu or Tencent.”

Khanna said federal tech policy should follow the precedent of the U.S. vs. Microsoft antitrust case and bar companies from using their platforms to benefit their other products at the expense of competition.

“I would say take that same precedent (and) make sure that companies can’t privilege their own platform,” Khanna said. One example: “It means that Amazon shouldn’t be able to privilege Amazon Basics.”

Tal Kopan is The San Francisco Chronicle’s Washington correspondent. Email: tal.kopan@sfchronicle.com Twitter: @talkopan