Trump in Phoenix: Prelude to policy statements?

As the city of Phoenix prepares for President Donald Trump's political rally on Tuesday evening, and protestors lay the ground-work for furious recriminations of the president, there are still questions about why he is coming to the city and what policies he may announce during the event. 

Last week, Trump's political campaign, still dialed up despite last November's win, announced that he would pay a visit to Phoenix. While it was likely that Trump had more than a general rallying of his base in mind, the campaign did not outline why he was coming. 

Some rumors suggested that Trump was considering pardoning the former sheriff of Maricopa County, Joe Arpaio — a move that the president said he was pondering. Others suggested that Trump may endorse a primary challenger to U.S. Sen. Jeff Flake, a Republican who has frequently criticized the president. State Treasurer Jeff DeWit, who worked on Trump's campaign in Arizona, has said he won't seek re-election, but his name has been floated as a potential challenger for Flake.

Flake spent the morning in Tucson, creating more than metaphorical distance between himself and Trump.

U.S. Rep. Raul Grijalva, a Tucson Democrat, said he was working to organize a protest outside Trump's rally, while U.S. Rep. Martha McSally confirmed to TucsonSentinel.com that she would not attend the Trump event.

Despite local political calculations, it's also possible that Trump will use the rally to return to one of his signature issues, pursuing the contraction of a wall along the U.S.-Mexico border. 

Trump will survey border equipment in Yuma, Arizona, including the Predator drone flown by U.S. Customs and Border Protection, and meet with members of the military at the Marine Corps Air Station before heading to his rally in Phoenix, the New York Times reported. 

He may visit the border, however, administration officials on a background call with reporters declined to confirm the visit. 

Last September, Trump used the same location as a candidate to slam the door on rumors that he was softening his immigration stance, launching into an effusive description of his plans for a "great wall" along the southern border. 

Trump said he would build an "impenetrable, powerful, solid southern border wall." 

This wall, would be paid for by Mexico "100 percent," he said. "They just don't know it yet," Trump said to cheers from the crowd. 

As yet, the wall has not be built, however, federal officials began laying the groundwork for parts of the wall in a national wildlife refuge in Texas. 

Congress appropriated $1.6 billion for the construction of some kind of border wall, though it seems increasingly likely, that rather than Trump's "impenetrable" and "solid" wall, Customs and Border Protection will build bollard fencing similar to structures in and around Nogales. 

Trump also outlined harsher immigration enforcement priorities, some of which have come to bear following a series of executive orders from the president in January and February. 

Yuma is a focal point for those who want to build more walls and infrastructure along the U.S.-Mexico because the city, and the surrounding Border Patrol sector was the site of a major construction effort in 2006 as part of the Secure Fence Act. In Yuma, federal officials fenced 107 miles of the sector's entire 126 mile border with Mexico, building dozens of miles of single and double-layer fencing to defend the border near Yuma and San Luis, Arizona. 

During the call, Trump aides touted their progress in a conference call with reporters to preview the trip, stating that illegal crossings along the U.S.-Mexico border have plummeted 46 percent in the first seven months of the year compared to the same period in 2016, reported the Washington Post. 

At the same time, the number of illegal immigrants removed from the interior of the country has increased by 32 percent, officials said. 

Apprehensions of unaccompanied minors are down 26 percent from the same time period last year, according to CBP statistics, however, the number of family units—or parents and guardians traveling with children—have risen 14 percent. 

In the Tucson Sector, which covers most of the state, just east of Yuma to the New Mexico border, apprehensions of unaccompanied children are down 45 percent, and apprehensions of family units are down 32 percent. 

However, this shift hasn't been uniform across the entire Southwest border. In El Paso Sector, which covers New Mexico and a chunk of Texas, the number of unaccompanied children is up 12 percent, while the number of family units has spiked to 102 percent compared to the same period a year earlier. 

Total apprehensions have continued to drop since a minor spike in May 2014 when nearly 69,000 people were caught by Border Patrol agents as they tried to cross the U.S.-Mexico border. However, this follows a larger, long term trend that has been happening since 2006 when nearly 1.2 million people were apprehended. 

Under the Obama administration, total apprehensions dropped 25 percent from 2009 to 2016, and this trend has continued through the Trump administration.