Make it a march for science, not a march by scientists. That’s the advice from a veteran science lobbyist to organizers planning a big public rally in Washington, D.C.

Michael Lubell is a physics professor at The City College of New York in New York City who, for 22 years until last month, was also head of the Washington, D.C., office of the American Physical Society. Over decades, he learned what kinds of messages resonated with lawmakers and the public—and among scientists. (Lubell was removed from his post after members criticized a 9 November 2016 press release from his shop that pledged to work with the newly elected U.S. president, Donald Trump.)

Scientific societies have so far taken a wait-and-see attitude publicly toward this week’s news of a grassroots effort to organize a march on Washington, D.C. (That includes AAAS, which publishes Science Insider.)

Organizers are meeting this weekend to plan strategy, including a date for the march and its goals. Lubell, who has no affiliation with the organizers, offers them three pieces of advice.

Make it a march about science, not scientists.

“The women’s march encompassed a lot of issues, and that was one of its strengths,” he says. “There are several important issues that the march could emphasize, including the value of a sustained investment in basic research, the need to preserve data access, the importance of science and math education in training a globally competitive workforce, and the role of science and technology in economic development.” The idea of “alternative facts” is anathema to science, he adds. “Alternative facts don’t exist in science, he says, “and we should fight against any attempt to bend facts to meet someone’s ideology.”

A big tent has downsides, but that can be dealt with.

“There’s certainly a risk of being associated with people espousing radical causes,” he says about scientific organizations that worry about protecting their reputations. “But there’s a risk from remaining silent, too. You don’t have to agree with everything that is being said and done. And I think most people would agree that, in the current political climate, sitting on the sidelines isn’t a very effective strategy.”

Every scientist who attends should bring along a nonscientist.

“Scientists are seen as an elite group, and perhaps even part of the establishment that so many people voted against in November,” he says. “And that attitude will be reinforced if the marchers are mostly a bunch of academic researchers. It would be better, for example, if they brought along a high school science teacher, someone who’s seen as being closer to the community. Otherwise they run the risk of looking like they are simply advocating for their own self-interest. If it’s done correctly, it could be terrific.”