Updated at 3:27 p.m. ET

President Trump is returning to a red-meat topic for his political base — building a border wall and cracking down on illegal immigration.

Before Trump rallies the faithful in Phoenix (and possibly also faces down protesters) at a campaign rally there Tuesday, he will check out a Predator drone and other equipment used by Customs and Border Protection to track and stop people from entering the country illegally.

Department of Homeland Security officials, in a call with reporters Tuesday morning, said Trump's stop in Yuma, Ariz., will allow him to highlight what can happen when a border wall (or, technically, a fence) is combined with additional enforcement resources.

Before 2006, there were only 5.2 miles of border fence in what's known as the Yuma sector. Now, there are 63 miles of fence and illegal border crossings are down more than 80 percent, according to the Department of Homeland Security.

"So investments in the wall, as well as other border infrastructure, law enforcement personnel and technology, as well as increased prosecutions all resulted in a steep drop in illegal border crossings," said an official with the department who declined to be named. "What was once one of the least secure border areas in America is now one of the most secure areas because of those investments in border security."

Vice President Pence told Fox News in a live interview Tuesday morning that the president will use his campaign rally in Phoenix to lay out his agenda for the weeks ahead as Congress prepares to return to Washington. "We want to build a wall and have internal enforcement and border security," Pence said.

"Illegal immigration at our southern border is down now more than 60 percent. And that's the result of the leadership that President Trump has been providing. But we need Congress to continue to support those efforts," Pence added.

There has been some discussion of demanding that funding for the wall be part of the government funding bills that must pass by the end of September. Others have talked about making it part of a deal to raise the debt ceiling, which also has a looming deadline. But it's not clear this is as high a priority for Republicans in Congress as it is for the president.

As Pence points out, illegal border crossings are down significantly under Trump. According to Department of Homeland Security statistics, from Jan. 1 to July 31, 2017, the Border Patrol apprehended 126,472 individuals attempting to illegally enter the U.S. at the border. That's a 46 percent decrease from the same period in 2016, which means fewer people are trying to enter the country now.

Trump is returning to the wall, one of the greatest hits of his campaign and something that had supporters chanting "build the wall" with zeal, just as he is taking hits from the far right for his decision to fire adviser Steve Bannon and to keep American forces in Afghanistan, apparently indefinitely. Trump is also still under fire from both the left and and from elected officials in his own party for his remarks about the recent violence in Charlottesville, Va., which led to the death of a 32-year-old woman.

And after two weeks of "working vacation" that included escalating tensions with North Korea, Venezuela and Republican senators, Trump is back to familiar territory with Tuesday night's "Make America Great Again" rally in Phoenix. But, previewing the president's speech, Pence indicated there will be more focus on his agenda in Congress than a more traditional Trump campaign speech.

"The message I think the president will deliver tonight is that we need to get on with the business of the American people. I mean, this president was elected to rebuild our military, to restore our economy, to make America safe again," Pence said on Fox And Friends. "And I think tonight you will hear the president say that, as the Congress prepares to come back, here's the agenda."

Pence will also attend Tuesday's rally.

Trump had raised speculation that he might use his trip to Arizona to pardon former Maricopa County Sheriff Joe Arpaio, who was recently convicted of contempt of court for refusing to stop targeting people for traffic stops who might be illegal immigrants. Trump told a Fox news contributor that he was "seriously considering" it, then retweeted the article about it.

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