When Rep. Bill Foster first decided to run for Congress in 2007, he did what many aspiring politicians do: He asked his friends for money.

For the Illinois Democrat, a former physicist at the Fermi National Accelerator Laboratory, many of those friends were scientists. They gave generously and have continued to give generously in his subsequent five elections. In fact, no candidate for U.S. Congress has raised more over the past 10 years from self-identified scientists and engineers than Foster, who took in $1.8 million in that time, according to an analysis of Federal Election Commission data.

“I am deep in the pocket of scientific truth,” Foster joked.

On Saturday, Foster plans to join the thousands of scientists and supporters of science who will take to the National Mall in Washington and to the streets in more than 400 communities across the world to assert the importance of science and protest American policies they see as detrimental to the field and to society. The march, organized in the wake of communication restrictions imposed by President Trump’s administration on government scientists and proposed federal budget cuts to scientific funding, has been described as an unprecedented moment of political engagement by the scientific community.

But scientists, such as those who donated to Foster, don’t necessarily keep politics at arm’s length to begin with. Over the past 10 years, FEC data shows, scientists and engineers have given more than $140 million to federal candidates and parties, with nearly 60 percent of that going to Democratic candidates and party committees.

This analysis considered donations to candidate committees and political parties by individual donors whose self-identified occupation fell within the disciplines of science, mathematics and engineering as identified by the National Science Foundation. Social scientists were excluded for the purpose of this analysis. The analysis also excluded donations to candidate-affiliated leadership and joint-fundraising committees as well as independent political groups, which often aren’t affiliated with a particular party. Donation amounts were adjusted for inflation to 2016 dollars. You can find the data on GitHub here.

Over the past decade, the scientific community has shown a willingness to support candidates with a science background. Seven of the 10 U.S. House candidates who received the most support from the scientific community have at least a bachelor’s degree in science or engineering, according to the analysis. After Foster, California Democrat Jerry McNerney, an engineer with a doctorate in mathematics, raised the second-largest amount: more than $460,000.

But scientists often abstain from political involvement, said Rush Holt, a former eight-term member of Congress and president of the American Association for the Advancement of Science, the largest professional organization of scientists in the world. Holt said that scientists avoid the political public square because they think it goes beyond their scope of expertise or worry that it could affect their funding or their ability to perform their work objectively. But he thinks those concerns are overblown.

“Scientists shouldn’t kid themselves in thinking that politics is dirty and science is pure and therefore tell themselves that they’re above politics,” Holt said.

When the scientific community does donate, presidential contenders have been the biggest beneficiaries, and scientists have handily favored Democratic candidates during the past three presidential contests. Barack Obama topped the list, taking in nearly $18 million from scientists and engineers during his two campaigns. Obama received more money in each of his elections than Hillary Clinton received in her unsuccessful bid last year.

Among Republicans, Mitt Romney raised the most, taking in more than $3.8 million in 2012. Last year, the scientific community — which includes politically generous engineers and geologists in Texas — gave more to Texas Sen. Ted Cruz’s campaign for president than they did to Trump’s.

Sen. Elizabeth Warren, of Massachusetts, and Wisconsinite Russ Feingold, both Democrats, have received the most support from scientists and engineers among Senate candidates — with roughly $600,000 going to Warren and more than $450,000 to Feingold over the past decade. Cruz and Scott Brown, who served in Massachusetts and lost a bid in New Hampshire, have been the top Republican Senate recipients, each taking in more than $375,000.

Scientists certainly aren’t as active as some other professions when it comes to political donations. They gave less than both self-identified doctors and lawyers, even though there are more than four times as many scientists and engineers as either doctors or lawyers in the U.S., according to the most recent data from the Bureau of Labor Statistics. Doctors gave roughly 90 percent more to political candidates and parties between 2007 and 2016 than scientists and engineers. Lawyers gave more in the 2016 cycle alone than scientists and engineers gave during the entire 10-year period.

And despite increased engagement by the scientific community now, political giving was only 3 percent higher in 2016 than in 2008, the last presidential election with no incumbent running, though the giving skewed more Democratic in 2016 than in any other cycle in the past 10 years.

You won’t find a lot of scientists in Congress. Foster is the only member with a doctoral degree in a scientific field. Two other House members have worked as scientists, and seven members of the House and one senator have worked as engineers, according to the Congressional Research Service.

Foster said Congress could use more members with scientific expertise. He points to technical guidance he provided to fellow politicians during deliberations over the Iran nuclear deal as an example of the kind of specialized knowledge scientists bring to politics.

“Almost all significant decisions that we face have a technological component,” he said.

Shaughnessy Naughton, a Pennsylvania Democrat and former drug researcher, wants to see more scientists take the plunge into politics. Naughton, who lost her races for the U.S. House in 2014 and 2016, has started a political nonprofit called 314 Action whose goal is to persuade scientists to run for office and to provide financial support.

“I think there is growing understanding in the scientific community that we need to go beyond signing petitions and letters and get involved in electoral politics,” she said.

Naughton’s group, which counts veteran Democratic strategist Joe Trippi among its board members, held a training session Thursday in Washington for scientists considering a run for office. The group says 80 prospective candidates attended the session.

The group currently supports only Democratic candidates, though Naughton said she hopes to establish a separate fund to support Republicans.

“When you look at the party platforms, particularly on climate change, there’s a stark difference,” Naughton said. “We felt like we had to pick a side.”

That’s in line with many scientists’ politics: Four out of five scientists identify as Democrats, according to a 2014 Pew Research Center survey of American Association for the Advancement of Science members, and more than half describe themselves as liberal or very liberal.

Comparatively, political givers in the scientific community skew less Democratic. That could be partly explained by differences between political donors and the rest of the population. An analysis of top political givers in 2014 by the Center for Responsive Politics found that people who donate to politics tended to be slightly more Republican overall.

But variations between scientific disciplines also account for some of the difference. Engineers were responsible for more than 70 percent of the overall giving by the scientific community from 2007 through 2016, and they showed a smaller preference for Democratic candidates and parties, giving 52 percent to Democrats and 46 percent to Republicans. From 2009 through 2014, engineers gave more to Republican candidates and party groups than Democrats.

While scientists accounted for less than 25 percent of total giving over the past decade, more than 70 percent of their money went to Democratic candidates and groups.

Despite the political leanings of scientists, nearly two-thirds of American adults don’t think that scientists have an ideological slant, according to a 2014 Pew survey. The findings were consistent with the same survey five years earlier.

Some in the scientific community worry that increased political activity and Saturday’s march could politicize science and make it a more partisan issue.

“It’s something I worry about a lot,” Foster said. “It shouldn’t be.”

Organizers say the march is nonpartisan, and they have chosen not to invite politicians to speak during the event. They emphasize that the march goes beyond particular grievances with the Trump administration.

“Anti-science policies have been enacted by people on both sides of the aisle for a very long time,” Caroline Weinberg, a health researcher and an organizer of the march, said at a recent event in Washington. “Acting as though this is a new thing is giving too much credit to this administration.”