Last year, UCLA grad student Michael LaCour and Columbia political scientist Donald Green published a startling finding, based on a experiment they ran: going door to door to try to persuade voters to support same-sex marriage works, they found, and it works especially well when the canvasser delivering the message is gay. They even found spillover effects: people who lived with voters who talked to a gay canvasser grew more supportive of same-sex marriage, too.Turns out, this exciting conclusion was a complete fraud.
This was a really exciting conclusion, for political scientists and laypeople alike. Past research has suggested that people's political views are tribal and largely impervious to rational persuasion. Dartmouth political scientist Brendan Nyhan and the University of Exeter's Jason Reifler have conducted multiple studies that show correcting people's incorrect views about, say, the presence of WMDs in Iraq can actually backfire and make them hold their wrong beliefs even more firmly.
The thing is, you really can engage reason and change people's minds about things. You just can't do it quickly. I've changed my mind about very many political questions over time, to include free trade (which sounded plausible before the evidence came in), abortion (I was against the practice personally but totally pro-choice before I began to study philosophy, and it is precisely thinking through the issue rationally that has convinced me that we should have much tighter legal restrictions on the practice), foreign policy (as a teenager and twenty-something I had isolationist sentiments that I've been reasoned out of over time), and so forth.
In the course of a single election cycle, though, you probably can't. Those tribal issues are algorithms we use to decide issues quickly, and most people don't pay attention to politics enough to do otherwise than decide when they really have to decide. So you get political responses that are more like, "Oh, yuck, he's in favor of it? I'm against it totally." Push people on this, and they'll push back harder because now you're trying to force them to do something they find gross and disgusting.
There's still reason to hope that persuasion and patient argument, or new evidence, will become persuasive over time. If there were not, there would be little reason to favor democratic forms of government.