Donald Trump's signature issue is immigration. When asked by the New York Times what he would accomplish during his first 100 days as President, Trump responded: "rescind Obama's executive orders on immigration," design the wall with Mexico, and ensure "the immigration ban on Muslims would be in place." Trump's immigration policy has five pillars.
Immigrants are dangerous: A January NBC News poll found that 34 percent of Republicans thought "terrorism" was the biggest issue facing the US; another 13 percent said it was "immigration." Trump has linked these two issues and staked out a position so extreme it outflanked the other GOP contenders, making him the presumptive Republican nominee.
In his June 15th announcement speech Trump said: "The U.S. has become a dumping ground for everybody else's problems" When Mexico sends its people, they're not sending their best" They're sending people that have lots of problems, and they're bringing those problems with us. They're bringing drugs. They're bringing crime. They're rapists."
On July 5th, Trump asserted that Mexicans were responsible for "tremendous infectious disease" pouring across the border." Trump's first TV ad implied that ISIS fighters were also "pouring across the border."
The non-partisan website Politifact judged Trump's claims to be false. (Politfact also noted, "there is no evidence of a massive influx of infections across the border.")
Immigrants take away jobs: In a July 11th speech,Trump made further claims about immigrants: "They're taking our jobs. They're taking our manufacturing jobs. They're taking our money."
According to an August Rasmussen poll 51 percent of Americans "believe illegal immigrants are taking jobs away from American citizens."
However, an August Forbes magazine article said this belief is incorrect: "illegal immigrants actually raise wages for documented/native workers."
Immigration can be stopped by building a wall along the Mexican border: Trump promises to build a wall along the open border with Mexico. When pressed, Trump said the wall would be 1000 miles long, rise 35-40 feet, and cost $8 billion.
The Washington Post studied Trump's wall design and estimated that it would cost $25 billion for design and material; in addition, the construction would require "40,000 workers per year for at least four years."
Trump insists Mexico must pay for this wall. If they do not, he promises Mexican citizens will be subject to penalties on remittance payments, tariffs on temporary visas, and increased fees on border-crossing cards and at ports-of-entry. Legal experts believe that Trump's reimbursement scheme is illegal.
However, the bigger concern is whether such a wall, if built, would accomplish its objectives. Politifact noted that, in recent years, there has been zero net immigration across the Mexican border -- that is, the number of folks going north is matched by the number of people going south. (This was confirmed in a November Pew Research report.)