No one is more perplexed by Donald Trump than the leaders of the Republican Party. On May 5, after Trump effectively clinched the Republican nomination, Paul Ryan famously asked:

Does he share our values and our principles on limited government, the proper role of the executive, adherence to the Constitution?

As the speaker of the Republican-dominated House, Ryan could have posed a harder question: Do Republican voters “share our values and our principles”?

The answer to this question, based at least on the 10.7 million votes cast for Trump in Republican primaries and caucuses so far, is “no.”

But that’s not all. There is also strong evidence that most traditional public opinion surveys inadvertently hide a segment of Trump’s supporters. Many voters are reluctant to admit to a live interviewer that they back a candidate who has adopted such divisive positions.

In matchups between Trump and Hillary Clinton, Trump does much better in polls conducted online, in which respondents click their answers on a computer screen, rather than in person-to-person landline and cellphone surveys.