Despite some recent stumbles in his campaign, the most dramatic development of the 2016 presidential race has been the meteoric ascent of Donald Trump to the status of front-runner for the Republican nomination. Trump’s rise is a particularly blatant example of a much deeper problem at the heart of modern democracy: widespread voter ignorance.

Trump’s success so far is in large part the result of an almost perfect storm of political ignorance. As a longtime celebrity, he had a built-in advantage with voters who don’t know much about politics, and therefore know little about more conventional politicians. With them, the name recognition that comes from being an entertainment celebrity is crucial.

Polls also consistently show that Trump’s support comes disproportionately from those with relatively low levels of education. For instance, a recent ABC/Washington Post survey found that 40% of Republican-leaning voters without college degrees support Trump, compared with only 19% of college graduates. Low education correlates with support for Trump far more than political ideology, or any other demographic variable. Education and political knowledge are not the same thing. Many college graduates know very little about politics, and some who lack college degrees know a lot. Nonetheless, the two are highly correlated.

Political ignorance could also help explain why Trump has won the support of a large share of the generally conservative Republican primary electorate, despite his long history of liberal stances on issues such as health care, taxes, government spending and property rights. Relatively ignorant voters rarely pay close attention to issue positions and are likely unaware of the details of Trump’s record.

Some argue that lesser-educated voters are attracted to Trump because of his anti-immigration platform. Americans with lower education could be more exposed to competition from immigrant workers. But many surveys show that there is little or no correlation between opposition to immigration and exposure to job competition from immigrants. Indeed, opposition to immigration is disproportionately high in states where the immigrant population is relatively small. Moreover, the people most exposed to competition from new immigrants are other recent immigrants with similar job skills. Yet immigrants consistently show stronger support for additional immigration than do native-born Americans.

In both the United States and Europe, support for tighter restrictions on immigration is highly correlated with ignorance about the true number of immigrants (restrictionists tend to greatly overestimate it) and with xenophobic hostility toward foreigners. Opposition to immigration is also often correlated with ignorance of economics. In his book The Myth of the Rational Voter, economist Bryan Caplan found that the economists on both the left and right take a far more favorable view of the impact of immigration on the economy than ordinary voters, particularly those who have low levels of education and economic knowledge. Economists understand that the economy is not a zero-sum game between immigrants and natives; rather, each group can benefit from the work of the other.

Anti-immigration voters might also be misled by claims that immigrants increase the crime rate, an assertion embodied in Trump’s notorious statement that Mexico is sending us “criminals” and “rapists.” In reality, studies consistently show that immigrants have a much lower violent crime rate than natives. Not all opposition to immigration is the result of ignorance. But a great deal is.

Unfortunately, political ignorance is not a problem unique to Trump’s supporters or this particular campaign, or to any one side of the political spectrum. Decades of survey data show that most Americans have low levels of political knowledge. For example, an Annenberg Public Policy Center survey taken during the 2014 campaign, which decided control of Congress, found that only 38% knew which party controlled the House of Representatives at the time, and the same low percentage knew which one controlled the Senate.

Exploitation of ignorance was a standard political tool long before Trump decided to run for president. It was not Trump but the far more respectable President Obama who secured passage of his signature health reform law in large part by manipulating what Obamacare architect Jonathan Gruber called “the stupidity of the American voter.” The president lied to the public when he repeatedly assured them that “if you like your health care plan, you can keep it.” A 2012 YG Policy Center poll showed that 64% of Americans fell for that deception.

The problem is not that voters are stupid, or that accurate information is unavailable. Rather, for most voters, political ignorance is actually rational. No matter how well-informed you are, the probability that your vote will change the outcome of an election is tiny — only one in 60 million in a presidential election. Few Americans know the exact odds. But most have an intuitive sense that there is little payoff to carefully studying political issues. Quite rationally, they act accordingly. That behavior, however, leaves them vulnerable to Trump and others who seek to manipulate ignorance for political gain.

Despite his current lead in the polls, Trump probably won’t win the GOP nomination, much less the presidency. But even when his star fades, the political ignorance that fueled his rise will remain, ripe for exploitation by other candidates and interest groups. That, far more than his crude rhetoric, is the truly frightening reality revealed by The Donald.