How ready the Republican electorate was for that message probably wasn't as obvious then as it should have been. The defeat of then-House Majority Leader Eric Cantor (Va.) in a 2014 GOP primary was pegged to his stance on immigration, but that wasn't necessarily the only reason. Trump has made the priority of the topic clear.

New data from the Public Religion Research Institute provides exhaustive documentation for why Trump's immigration message found a willing audience with Republicans. Trump's strength with the party -- a party that is mostly white and skews older -- has largely been with less educated voters. He's done surprisingly well with evangelicals, too -- a group once thought to be solid for Ted Cruz. PRRI's data shows that those groups are ones more likely to view immigration as a threat to American culture and values than as a beneficial force.

Take age, for example. Far more older Americans view immigration as a threat than do younger ones.

Fewer than half of white Americans think that immigration benefits the country…

…though the same age split plays out there, too. More importantly, less-educated white Americans are more likely to view immigration as a threat, and that's a key constituency in Trump's rise in the nomination contest.

There's overlap with age, race and political identity, of course, so it shouldn't be a surprise that conservative Republicans are the group most likely to view immigration as a threat to traditional values. This is also a group with which Trump has done better than expected -- though more moderate Republicans have been a bigger source of support overall.

Among religious groups, more than half of white evangelical Protestants think that immigrants threaten traditional American values. Mormons -- a group that soundly rejected Trump in Utah last week -- are one of the least likely mostly white religious groups to view immigration negatively.

Trump's geographic support has been diverse, winning states across the country. But he's done particularly well in the South, where attitudes about immigration tend to be more negative. (It's also more religious and more conservative, of course, which overlaps.)

This is hardly entirely predictive. Wyoming, for example, went for Ted Cruz by a wide margin in voting. It's also not clear how much of a chicken-and-egg situation we have. Are less-educated whites Trump fans and therefore more anti-immigration or vice versa?

It's clear, though, that a Republican with a strong immigration message was well-positioned to be successful nationally this year.