Donald Trump’s rally speech in Phoenix on August 22 was full of falsehoods. He gave a revisionist and false history of his reaction to the Charlottesville violence to make himself look better, made false statements about media reporting and misled the audience over his economic achievements. The speech points to the normalization of post-truth politics, when appeals to personal beliefs and emotions wins out over objective facts. To avoid this normalization, we need to borrow the successful tactics of the environmental movement.

The rally speech represents part of a broader pattern: Of Trump’s statements fact-checked by Politifact, an astounding 49 percent are false. By comparison, his Democratic opponent in the U.S. presidential election, Hillary Clinton, has 12 percent of her fact checked statements rated false; 14 percent of Republican Speaker of the House Paul Ryan’s are.

Despite Trump’s extremely high rate of deception, many still believe him. As an example, 44 percent of those polled believed his falsehoods about Obama wiretapping Trump Tower during the 2016 election campaign. Thus, many will believe his Phoenix rally claims, despite the debunking by fact checkers. Unfortunately, 29 percent of the public, and only 12 percent of Trump supporters, trust fact checkers.


Moreover, research on debunking falsehoods shows such debunking sometimes backfires. Called the backfire effect, scientists have shown in a number of cases people believe in falsehoods even more strongly after being presented with contradictory evidence. This situation enables Trump to pollute our politics with deception, destroying trust in our democratic political system.

Political and social science research summarized in the 2003 Trust and Governance, edited by Valerie Braithwaite and Margaret Levi, shows trust is vital for healthy democracies. Citizens in a democracy have a basic expectation of their public officials being trustworthy, in their words and actions. In return, citizens comply with laws, pay taxes and cooperate with other government initiatives. By comparison to a democracy, an autocratic state bears a much higher resource burden of policing to make its citizens comply with its laws. In his 2002 work, Trust and Trustworthiness, political scientist Russell Hardin also shows the vital role of trust in creating and cultivating civil society in a democracy. When political leaders act in ways that destroy trust—as Trump is doing through misleading statements and outright lies—people will increasingly stop complying with laws, paying taxes and engaging in civil society. Trump’s actions are fatally undermining the health of our democracy.

His behavior falls within the sphere of what behavioral scientists term “tragedy of the commons,” following a famous 1968 article in Science by Garret Hardin. Hardin demonstrated that in areas where a group of people share a common resource—the commons—without any controls on the…