STEVE INSKEEP, HOST:
There is a caravan of several thousand Central American migrants moving through Mexico, some of whom may reach the United States. In the broad sweep of immigration, it's not that big an issue. But President Trump, through tweets and rally speeches, is making sure everybody knows about it.
(SOUNDBITE OF RALLY)
PRESIDENT DONALD TRUMP: That is an assault on our country. That's an assault.
UNIDENTIFIED PEOPLE: (Cheering).
TRUMP: And in that caravan, you have some very bad people. You have some very bad people. And we can't let that happen to our country.
INSKEEP: The president offered no evidence for that claim, nor did the White House back it up. As NPR White House correspondent Tamara Keith reports, his statements are no accident.
(SOUNDBITE OF RALLY)
UNIDENTIFIED PEOPLE: (Chanting) Build the wall.
TRUMP: That's happening.
UNIDENTIFIED PEOPLE: (Chanting) Build the wall. Build the wall.
TAMARA KEITH, BYLINE: Chants of build the wall roared inside the Houston arena where President Trump rallied the faithful last night.
(SOUNDBITE OF RALLY)
UNIDENTIFIED PEOPLE: (Chanting) Build the wall. Build the wall.
KEITH: In recent days, the caravan of migrants has become a key feature of Trump's rally speeches. Democrats are to blame, he says, and Republicans, of course, will be the saviors.
(SOUNDBITE OF RALLY)
TRUMP: We will end sanctuary cities, stop catch and release, visa lottery - chain migration, out. And we will keep the criminals, drug dealers, and terrorists the hell out of our country.
UNIDENTIFIED PEOPLE: (Cheering).
KEITH: Go back to 2015 and the day Trump rode an escalator in Trump Tower into the race for president, and his rhetoric is little-changed.
(SOUNDBITE OF ARCHIVED RECORDING)
TRUMP: They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people.
KEITH: He was asked about those comments in 2016 in a sworn deposition. And Trump's response reveals something about how he sees immigration as a political tool.
(SOUNDBITE OF ARCHIVED RECORDING)
TRUMP: Illegal immigrants, yes, illegal immigrants...
DEBORAH BAUM: And I...
TRUMP: ...Which is a very big topic in this country. And which is a topic that, you know, has led to my nomination in a major party in the country.
KEITH: Recent polls show that for Republican voters, illegal immigration remains a top concern.
MARC SHORT: It is a political winner for the president heading into the midterms.
KEITH: Marc Short was White House director of legislative affairs in the Trump administration and is now a senior fellow at the Miller Center.
SHORT: Americans still want border security. And I think as they see images on TV of the caravan coming, that it reminds them of the need to have border security. Politically, it does work to the president's benefit right now.
KEITH: The irony is immigration is an area of great frustration for Trump. Border crossings haven't fallen long-term. The wall isn't fully funded by Congress - or Mexico, for that matter. And efforts to work with Congress to change immigration laws failed. Daniel Garza is president of the LIBRE Initiative, which is part of the Koch political network.
DANIEL GARZA: It does activate the base. It gives them a sense of passion, you know, for, you know, the things that they believe in. And in that sense, he's winning. But you have to govern.
KEITH: But this is peak election season. And governing isn't the immediate goal. Two weeks out, it's all about boosting the base. And President Trump has found again and again that illegal immigration is a powerful motivator for his supporters.
Tamara Keith, NPR News.
(SOUNDBITE OF TEN WALLS' "SPARTA") Transcript provided by NPR, Copyright NPR.
