The October issue of Scientific American will carry what has never been seen in the magazine's pages in 175 years: A presidential endorsement. 

In an urgent and impassioned editorial first published online Tuesday, the editorial board endorsed former Vice President Joe Biden, the Democratic nominee, calling him the candidate "who is offering fact-based plans to protect our health, our economy and the environment."

It was a striking move for the oldest continuously published magazine in the United States and one its editor in chief, Laura Helmuth, said was both carefully considered and entirely necessary. (Helmuth previously worked as The Washington Post's science editor.)

Four years ago, the magazine flagged Trump's disdain for science as "frightening," but did not go so far as to endorse his rival, Hillary Clinton. This year, its editors came to a different conclusion.

"A 175-year tradition is not something you break lightly," Helmuth told The Post Tuesday. "We'd love to stay out of politics, but this president has been so anti-science that we can't ignore it."

The endorsement is one of several occasions during the president's tenure when the scientific community has denounced Trump's beliefs and policies. The 2017 March for Science rallied the community to defend its institutions from budget cuts and undermining by Trump and his appointees. A growing movement to get scientists to run for political office emerged ahead of the 2018 midterm elections. Most recently in May, the medical journal the Lancet blasted Trump in an editorial for his "inconsistent and incoherent" coronavirus response.

Scientific American's 1,400 word editorial is as much an endorsement of Biden as it is a catalogue of  Trump's hostility to science throughout his term.

"The evidence and the science show that Donald Trump has badly damaged the U.S. and its people - because he rejects evidence and science," the endorsement reads, citing his push to eliminate health rules from the Environmental Protection Agency, reject stricter air pollution standards and his continued denial of climate change.

In a nod to Trump's embrace of anti-science conspiracy theories, Scientific American editors contrasted who each candidate turns to for expertise and insight: Biden's panel of public health advisers include figures like former U.S. Food and Drug Administration chief David Kessler, and immunologist Rebecca Katz.

"It does not include physicians who believe in aliens and debunked virus therapies, one of whom Trump has called 'very respected" and "spectacular,' " the editors write.

Ultimately, it was Trump's response to coronavirus that created a new sense of urgency for the Scientific American's editors, Helmuth said.

"We've seen the consequences of this so tragically with the coronavirus pandemic. It will be 200,000 people who have died from the virus, and a lot of that is on his hands," Helmuth said of Trump.

Despite the excoriation of the president for his anti-science stance, Helmuth stressed that the editors wanted their endorsement to be fact-based and evidenced-backed - not partisan.

"We never used the world 'Republican' or 'Democrat;' it's strictly about these two people," Helmuth said.

In such a politically fractured environment, Helmuth acknowledged that editors were concerned how an endorsement might read, and if it would undermine the public's faith in scientific institutions like theirs.

Scientific American's track record of not endorsing a candidate is what could ultimately give its endorsement more weight, according to Paul Beck, a political scientist and professor emeritus at Ohio State University.

"An endorsement from an organization like that - that has been in the past above politics - would carry considerable weight with their audience," Beck told The Post, calling the Scientific American endorsement "powerful."

For an organization that has avoided political endorsements for so long to join the fray is unusual, Beck said - though when it comes to the 2020 race, he said nothing surprises him.

"You have a truly anti-science president," Beck said, "and the scientific community by and large has been appalled at what has come out of the president's mouth and come out of Washington."

The fractured news environments and hyper-partisanship of American politics has faded the power of political endorsements compared to election cycles past, Beck said. Endorsements could still have an effect on undecided voters, whom he estimated a small percentage of the electorate, in the realm of 10 percent or fewer.

When it comes to potential Trump voters, an endorsement from a respected outlet like Scientific American won't move the die-hard supporters, he said, but it might sway Republicans or Independents who already have doubts.

"You can imagine if I'm a subscriber to Scientific American, and a Republican, I might say, 'well see, maybe I shouldn't vote Republican this time around,'" Beck said.

Helmuth said that after careful consideration of what an endorsement would mean, the decision by Scientific American's editorial board was ultimately unanimous.

"We cover the intersection of scientific issues that have political relevance," she said, "but this is the first time we've said, 'if you care about science and you're a voter, there's an obvious choice.'"