A small crowd gathered on Saturday outside the Ministry of Defence in Westminster, just across from Downing Street, for the second iteration of the March for Science. Last year’s event, which nucleated around the specific threat posed to American scientists by the incoming Trump administration, drew tens of thousands of people to Washington DC, and more than a million more across 200 cities worldwide. The number in London was reported to be 10,000.

This year there were fewer than a hundred. They waved homemade signs and cheered a series of speakers beneath the statue of Field Marshal Montgomery, but there was a definite sense that energy had been lost. ‘Last year we closed down the streets from the Science Museum to Parliament Square,’ a Cambridge paleoceanographer told me. ‘It was incredible.’ People recalled a sort of siege mentality. ‘Trump had just banned the EPA from tweeting and talking to the media,’ a UCL climate researcher said. ‘No one knew what was going to happen.’ Everyone was angry at Trump, and the British scientists talked about their fears around Brexit.

There is a sense among scientists that their work is being sidelined, and that their particular claim to the truth is losing influence – that there is substance to Michael Gove’s remark that people ‘have had enough of experts’. But even the original march, in the time between its conception and its execution, had somehow moved away from that locus, which centered on Trump, and became a mass international demonstration celebrating and reaffirming the general goodness of science. It is difficult to sustain a political movement with such vague demands. The people in London were hopeful on Saturday that the march in DC would attract a bigger crowd, but there, too, the numbers dropped, to a few thousand.

Scientists are right to worry. Polls suggest that public trust in science remains high, but in the past two decades democratic governments have suppressed and restricted scientists. The Bush administration did its best to silence climate researchers, and Stephen Harper’s government in Canada prevented federal scientists from talking to the media without permission. An anti-science PR strategy developed by climate change deniers has shown that exploiting false-equivalence in the media and attacking scientists’ personal credibility is remarkably effective. BBC Radio 4 was recently found to have broken accuracy rules for not challenging Nigel Lawson’s climate change denial in an interview last year.

But scientists’ default political stance is a wary one. The geologist Robert S. Young warned in the New York Times last year that a march ‘will serve only to trivialise and politicise the science we care so much about’, and turn scientists into ‘another group caught up in the culture wars’. There is a deeply held belief that even though science may be under threat from politics, political engagement by scientists would be even more damaging to their credibility. And so the response to a direct, defined political threat is an abstract call for the retrenchment of scientists’ special position as neutral but respected advisers to an imagined informed public.

The idea of a barrier between science and politics is no more than fifty years old. Scientists have always imagined themselves a world apart, but in the mid-20th century they regularly organised around political causes. In 1964, more than 50,000 people joined Scientists and Engineers for Johnson-Humphrey, and funded radio ads against the Goldwater campaign. ‘By the time we were through, any guy in Pittsburgh in a T-shirt with a can of beer in his hand knew the smartest people in this country considered Goldwater unfit,’ David Garth, a political adviser to the campaign, later said. The UK has had a long tradition of openly Marxist and socialist scientists who organised around their political leanings, including J.D. Bernal and P.M.S. Blackett.

The risks posed by Trump aren’t going away. He recently appointed Mike Pompeo, who has repeatedly denied the reality of climate change, as secretary of state. And Scott Pruitt has spent the past year gutting the Environmental Protection Agency. The model of the scientist as a neutral adviser who agitates only for funding has served researchers well, but left them with a lack of political options in a real crisis. For the moment, scientists seem content to take the long view, and to frame the dangers of ignoring them in terms of future disasters of climate or disease, rather than any immediate political consequences.