People wait in line to enter a campaign rally with Republican presidential candidate Donald Trump at Dordt College on Jan. 23, 2016, in Sioux Center, Iowa. (AP Photo/Evan Vucci)

There is considerable evidence that Donald Trump has built his national lead in the Republican president primary on a powerful combination of economic anxiety, frustration with Washington and, in particular, concerns over immigration. Interviews with voters reveal it again and again, and so do public opinion polls.

You can see signs of it in this nifty new Wall Street Journal interactive that shows 4 out of 5 Trump supporters believe immigration (not just illegal immigration — all immigration) hurts the United States more than it helps. A majority say free trade is bad for America. Other groups of GOP voters look more kindly on trade and immigrants.

More directly, two questions in the latest Washington Post-ABC News poll show how Trump is drawing lopsided support in the Republican field from voters who worry about the economy and about immigrants.

The poll asked respondents how concerned they are that they will be able to maintain their current standard of living. That's a straightforward test of whether people believe their personal economic situation is likely to improve or get worse. A quarter of Republicans said they're very worried about maintaining that standard of living. And Trump is winning a wide plurality of those voters — 42 percent. Among those who are not worried, he's winning only 28 percent. That's a statistically significant difference, according to The Post's polling guru Scott Clement.

No other candidate has a statistically significant difference in support between those groups. This suggests Trump is playing exceptionally well among the most economically anxious Republican voters.

Crosstab(40)

The divide grows even more on immigration. The poll asked whether immigrants mainly strengthen or weaken American society. Trump barely leads among Republicans who say immigrants strengthen America. But he holds a 33-point lead — commanding a solid majority — among Republicans who strongly believe immigrants weaken society.

Crosstab41

Trump also draws a majority of Republicans who say they want a political outsider to be the next president, compared to 18 percent of those who want someone with experience working in the system.

Those numbers suggest that Trump is winning because he has tapped into a particular set of concerns and dominated his rivals on all of them. Indeed, the Post-ABC poll finds a majority of Republicans trust Trump more than any candidate to handle the economy and bring needed change to Washington. A near majority trusts him the most on immigration and on terrorism (an issue he has repeatedly linked to immigration). He fares worse on the question of which candidate is closest to you on issues in general and which would best handle an international crisis. But those questions do not appear to be moving voters to the same degree.