The U.S. public’s vision for the government’s size and scope is “the most liberal ever recorded” in the 68-year history of what’s known as the Public Policy Mood estimate, the estimate’s creator James Stimson announced Wednesday.

“The annual estimate for 2018 is the most liberal ever recorded in the 68 year history of Mood, just slightly higher than the previous high point of 1961,” Stimson wrote to POLMETH, the mailing list of the Society for Political Methodology and the Political Methodology section of the American Political Science Association.

Stimson is a recently retired professor of political science at the University of North Carolina at Chapel Hill who has long measured the public’s view of government by comparing survey responses from over the decades and, in essence, putting them into an algorithmic blender in order to compare the public mood at different times on a continuum from left to right.

Stimson wrote Wednesday that the shift represents “expected leftward movement” in response to Donald Trump’s presidency. He cautioned, however, that his estimates “do not include Trump’s signature issues of immigration restriction and trade protectionism.”

Stimson also noted that a two-year measure of public mood, which combined data from 2017 and 2018 (and in similar two-year increments back to 1951/2) “shows the same leftward movement, but the 2018 level is not as left as the early 1960s estimates.”

Stimson’s public policy mood measurement addresses a problem in long-term public opinion analysis: the lack of common survey questions. As he wrote recently, “the actual agenda of politics changes over time and so survey organizations, trying to stay current, change the questions they pose.”

In other words, while political scientists aren’t lucky enough to have decades of pollsters who’ve asked about, for example, both McCarthyism and climate change, “the tracks of issue preferences over time should move together, tracing more or less parallel courses,” as Stimson wrote in 1991.

The Dartmouth political scientist Brendan Nyhan flagged Stimson’s most recent data on Twitter and noted their importance for 2020 Democratic presidential candidates.

Critical contextual factor for a future Democratic president if they defeat Trump in 2020 – see my @UpshotNYT on how LBJ benefitted from public demand for more government https://t.co/Ch3DrJTBo2 https://t.co/3x2di4n5aS — Brendan Nyhan (@BrendanNyhan) June 5, 2019

As Nyhan wrote in 2014, noting that Stimson’s data at the time indicated the public policy mood had shifted to the right, “What we perceive as presidential leadership (or lack of it) often reflects structural factors that are largely beyond the control of the chief executive himself — a reality of presidential power that critics of Mr. Obama’s speechmaking and relations with Congress often fail to appreciate.”