We Americans like to think of ourselves as political freethinkers who, confronting the questions of the day, use values and evidence to arrive at our individualized answers. But a body of research strongly suggests another possibility: Most of the time, we end up with the opinions we have because we’re parroting figures in our parties.
By this account — advanced most persuasively by the political scientist Matthew Levendusky — most people simply don’t take the time to work out their own position on every issue. More often, they pick a party, then wait for what academics called “partisan signaling”: messages from party leaders about the “right” opinions to have. Voters hear the party line, then sort their opinions to match — and the more ideologically homogenous the party’s leaders become, the more effectively their signals come through.
As recently as the 1970s, partisan signaling was weak: There were liberal “Rockefeller Republicans” and conservative Southern Democrats. Starting in the ’90s, each party’s signals got stronger, and partisan sorting — the alignment of individuals’ ideologies with their party — has surged since. (As a corollary, split-ticket voting has declined.)
Donald Trump presents an interesting case. On issues like international trade, he is wildly out of step with Republican leaders’ longstanding consensus. So far, Republican voters seem to be following him: An August 2016 Pew Research poll shows dramatic reversals in their appraisals of free trade compared to recent years, supporting Levendusky’s theory. But once the Trump presidency is underway, what will happen if, on trade or other issues, the White House and Congress send different signals? It’s something that we don’t have a lot of recent experience with, Levendusky says, “but the presidency gives you an awful strong signal. I’d probably give Trump the edge.”