Donald Trump speaks during a campaign rally on Aug. 13 at Sacred Heart University in Fairfield, Conn. (Evan Vucci/AP)

A number of scholars have argued that Donald Trump is a populist. What, if anything, does this label tell us about what we might expect from a Trump presidency? Would we see the erosion of judicial independence and congressional checks and balances? Would freedom of the press be curtailed? What would happen to democratic rights and freedoms more broadly?

For the first time, based on two separate research projects, we have systematic comparative evidence about what happens to democracy when populists come to power. This doesn’t allow us to predict precisely how any individual candidate — for instance, Trump — would behave in office. And the institutions of U.S. democracy — including the strength of opposition — are more robust than in other countries that have fallen under the sway of populists.

But if populist rule in the United States were to look like it does elsewhere, this would be of serious concern.

What is populism?

Populism is a political discourse that imagines a struggle between a good and virtuous “people” and a nefarious establishment. A populist is a charismatic leader who uses this kind of thinking to mobilize large numbers of people to gain and hold power. Populists can be either on the left or on the right; the outlook combines with a variety of other ideologies or issues.

Populists have achieved extraordinary success around the world in the past 30 years, with Hugo Chávez in Venezuela and Silvio Berlusconi in Italy being two of the best-known cases. We have each analyzed this historical record to learn what happens to democracy when populists come to power.

In one study, Paul Kenny (with Christian Houle) examined populist and non-populist governments in Latin America from 1982 to 2012. In another, Kirk Hawkins and Saskia Ruth (with Nathaniel Allred) analyzed the impact of populist rule on liberal democracy in Europe and the Americas in the 21st century. Although our analyses were conducted using slightly different measures of populism and different statistical models, we had very similar findings. The results are sobering.

1. Checks and balances on the executive branch are eroded

Ordinarily, even in presidential systems, legislatures oversee a range of government functions, such as approving budgets, sanctioning treaties and giving the authority for war. Courts uphold the rule of law, free from arbitrary political interference. In many democracies, other government institutions — electoral agencies, central banks or ombudsmen — have partial independence so they can protect government functions from partisan bias. Liberal democracy relies on these institutional and legal constraints on the executive branch.

Populists systematically evade and override these checks on executive power. Populist presidents in Peru, Venezuela and elsewhere have stacked judiciaries and overridden constitutional term limits. Ecuador’s Rafael Correa rewrote the country’s constitution, emasculating the Congress in the process.

These cases are not exceptions. While it’s hard to put a precise number on the extent of this decline, Houle and Kenny, using a common measure of judicial independence, find that after four years of populist rule, courts have 34 percent less independence than they would have under a typical democratic government. Using a broader measure of constraints on the executive — an index that includes several of the institutional checks and balances noted above — they find that after four years of populist rule, these checks on the executive are 17 percent lower than under a regular democracy, while the rule of law is 22 lower.

2. There’s less media freedom

Even the most minimal democracy has to be guarded by certain protections for free speech or it won’t function properly. If citizens cannot communicate freely and if the media can’t report on the government’s actions, the government cannot be held to proper account.

However, populists are unusually sensitive to criticism from the media, which they see as elite subversion of the people’s will, and they frequently threaten or restrict media outlets. Examples abound. In Turkey, Recep Tayyip Erdogan has imposed such draconian restrictions on media freedom that virtually any criticism of the president is a criminal offense — and these restrictions have gotten stronger in the crackdown after the recent coup attempt.

Using a common measure of media freedom, Allred, Hawkins, and Ruth find that on average, two terms of populist rule resulted in a 13 percent decline in media freedom.

3. Civil liberties are lost

Civil liberties refer to freedom of expression and belief; rights to associate freely and form organizations, and personal autonomy and other individual rights. Civil liberties in Venezuela have been increasingly constrained under the government of Chávez and Maduro, with NGOs and other critics of the government facing regular harassment and legal sanctions.

Allred, Hawkins, and Ruth found that civil liberties decline systematically under populist rule. Using a standard index of civil liberties, they found that two terms of populist rule resulted in a decline of 9 percent.

4. The quality of elections declines

For democracy to work, incumbents and challengers must play by the same rules. Incumbents can’t use their power to change the electoral rules, grab more campaign funding from the public trough, or get more media exposure through state-controlled outlets.

Because populists see their opponents in diabolical terms, and because they think they represent a unified will of the people, they are tempted to violate these rules. In Hungary, the government of Viktor Orbán adapted new electoral rules that benefited the ruling party and passed constitutional amendments that constrained the opposition’s political advertising.

Using a cross-national data set, Allred, Hawkins, and Ruth find that on average, after two terms of populist rule, the quality of elections declines by 15 percent.

Might this happen in the U.S.?

Of course, we can’t be sure that what happened under populist rule elsewhere would necessarily happen in the United States, which may have stronger safeguards against tyranny. But on average, under populist rule, press freedom, the autonomy of the judiciary, civil liberties and even the integrity of the electoral process all suffer.

Paul Kenny is research fellow in political and social change at the Australian National University.

Kirk Hawkins is associate professor of political science at Brigham Young University and the coordinator of Team Populism.

Saskia Ruth is postdoctoral fellow in political science at the NCCR Democracy at the University of Zurich and the Center for Democracy Studies in Aarau, Switzerland.