So what explains the chasm between these particular candidates’ online versus live polling data? It turns out that a nontrivial share of these same working-class, anti-immigrant voters won’t tell a live person who they support but will share their true feelings when their support is secret—like on Election Day. This is no surprise: Support for immigration and globalization are perhaps the only political sentiments that unite elites from both business and the academy, from right and left. Openly supporting an anti-immigration candidate can risk social opprobrium, ridicule, or worse. In other words, for every group of vocal Trump supporters, there are probably a lot more who just don’t advertise it.

One example comes from the United Kingdom Independence Party, or UKIP, which rose to prominence in the run-up to this May’s general election on a staunchly anti-immigrant and anti-EU platform. Polls there showed that at its height, online and automated polls gave UKIP a third higher level of support (16 percent) than did live-interview phone polls (12 percent). UKIP’s support dropped as Election Day neared, but this online/live-polling gap was evident even in the final polls before Election Day. The final polls from the country’s major online pollsters gave UKIP an average of 14 percent while the phone pollsters gave the party slightly over 11 percent. (The actual results split the difference between the two modes, as UKIP candidates received 12.7 percent of the vote.)

Anti-immigration, working-class parties elsewhere also do better in online polls. Current Swedish polls are divided by mode, too: Two prominent Internet pollsters show the virulently anti-immigrant Sweden Democrats leading with about 27 percent while other live pollsters show it in third place with about 19 percent. Plus, these anti-immigrant parties also typically outperform their final polling averages when the votes are counted. Both the Sweden Democrats and the Danish People’s Party outperformed their respective final-polling averages by about 3 percent in those countries’ most recent general elections, while the True Finns did about 1 percent better at the voting booth than in the polls.

Which is why Trump is on track to do much better than many of his detractors think; he’ll likely be much closer to the Internet and automated polls, where his lead is in the double digits, than the live polls, where his lead is still in the single digits.

This doesn’t mean Trump is on his way to the nomination. Public Policy Polling, an automated robocall pollster, consistently poses hypothetical one-on-one matchups between Trump and other GOP candidates. Though Trump regularly trashes Jeb Bush, Trump loses or runs roughly even with Bush in the Public Policy Polling one-on-ones. And it’s the same with all the other Republican candidates. Even when poll respondents are assured anonymity, there is simply a hard ceiling of support an anti-immigrant candidate can receive. When the field is more limited, Trump loses his edge. (General-election polls also show Trump does worse against the likely Democratic nominee Hillary Clinton than other leading Republican contenders do.)