The effort by Ionannidis and scientific colleagues to directly influence the president on a matter of scientific policy is not unprecedented. There have been many attempts by other scientists to do so in the past. Some sucessful, some not & some w/unanticipated consequences…
The most famous example is from Albert Einstein warming Roosevelt about the dangers of Germany developing an atomic bomb in 1939. dannen.com/ae-fdr.html 
But note that large scale efforts in the US (that became the Manhattan project) did not happen for another two years, after Pearl Harbor.
The climate example (you knew there was one) is curious. In 1972 as the Milankovitch theory of ice ages started to be supported by evidence from ocean drilling & as there had been a slight cooling in the northern hemisphere from the 1940s to 1970, some ppl linked them.
Notably there was a meeting in 1972 at Brown University organized by George Kukla that focused on the question of when the next ice age would start. Some of the attendees felt that it was imminent (at least geologically speaking). Others disagreed. en.m.wikipedia.org/wiki/Global_co…
But as a consequence of the meeting , George Kukla and Robert Matthews decide to write to the President (Nixon) to let him know of their “surprising result” that there was a danger of return to glacial conditions in “a century”.
Now, this was far from a consensus conclusion. Most scientists working in the area thought this was very premature given the state of the science (and more papers were being published predicting warming because of the increase in CO2). journals.ametsoc.org/bams/article/8…
But the ways of the federal govt. are mysterious. And while it’s unclear if the letter ever made it to the President’s desk, it did get some attention at State, and specifically it was referred to the Interdepartmental Committee for Atmospheric Science (ICAS).
(I should note at this point that while I’ve known about the Kukla/Matthews letter for a while, I only found out what happened to it recently, and mainly from this presentation from Robert Reeves: cpc.ncep.noaa.gov/products/outre… )
So ICAS decides to set up an “ad hoc Panel on the Present Interglacial” to look into it. By mid-1973 this panel decides to rewrite its terms of reference to expand its scope to climate variation in general. The report came out in Aug 1974… babel.hathitrust.org/cgi/pt?id=uc1.…
The report is far less definitive than the Kukla letter. They conclude that near-term prediction on the basis of Milankovitch forcing is highly uncertain & that short term predictions based on looking at spectra in the instrumental record “probably will not” work. Particularly…
…since the “interference” through human activities will more likely lead to a prolongation of the interglacial than its termination.
The only really actionable recommendation is to set up “A National Program for the Study and Prediction of Climate Fluctuations and their Impact on Human Affairs”. This gets taken up Commerce, and draft agency plan for a US Climate Program is out by Dec 1974. (Link?)
Various iterations of this plan knock about - the 1977 version is available here: books.google.com/books?id=R6cJA… And by 1977/78 legislation is passed to set up the National Climate Program office and CDC at NOAA.
So, did all of the subsequent apparatus of the federal government to work on climate research arise from a single letter by concerned (though overconfident & ultimately incorrect) scientists? No. Lots of other elements played a role - but it might have helped nudge things along…
