With a new poll showing him in a virtual tie with Republican frontrunner Donald Trump, Ben Carson went on the Sunday news shows to talk politics. On ABC’s This Week, host Martha Raddatz grilled Carson about some of his comments on immigration.

Carson, a resident of West Palm Beach, Fla., said he gets his information on immigration from local sheriffs and that he doesn’t trust figures from the federal government.

"You know, a lot of these people who are captured, it's ICE (Immigration and Customs Enforcement) who comes along and says, you must release these people. And that's not helpful to the American people. They need to be working for the American people, not against them," Carson said.

"We've had examples like in Yuma County where we've been able to stop 97 percent of the illegal flow, and those programs, they abolish," Carson added. "They don't want that. What is wrong with them?"

We too wondered why the government would abolish programs as effective as Carson said. So we checked it out, and found a lot more to the story of what was going on in Yuma County, Ariz.

97 percent

The first thing we noticed about Carson’s statement was that it didn’t include a time frame.

As we reviewed statistics about border apprehensions, we did find a precipitous drop in immigration for Yuma County, but it took place over at least a decade. And the drop matched the movement of the U.S. economy as it went from economic good times to deep recession.

The U.S. Border Patrol reported that total illegal alien apprehensions in the Yuma area went from 138,438 in 2005 to 5,902 in 2014, a decline of 96 percent. (The entire Southwest border saw a decline of 59 percent during the same time period.)

A report from the Congressional Research Service, the nonpartisan research arm of Congress, documented the decreases at Yuma and in other places since 1986; it noted that pinning down the precise causes of the decline in illegal immigration are difficult.

"The only significant decrease in unauthorized migration appears to have occurred since 2007, and it is unclear how much of the drop-off is due to increased enforcement and how much is a result of the U.S. economic downturn and other systemic factors," the report noted.

A 2014 report in the Yuma Sun noted the low number of apprehensions in the Yuma sector, but credited it primarily to increased funding for border security, specifically more money for border fencing with special technology and more agents.

Abolished program

Carson made reference to effective programs that had been "abolished." The closest thing we could find was a federal program aimed at prosecuting illegal immigrants that was scaled back, but not abolished.

The program, called Operation Streamline, aimed to aggressively prosecute all those who attempted to illegally cross the border, including nonviolent, first-time offenders. Yuma County Sheriff Larry Leon Wilmot said he received notice from the U.S. attorney’s office that the program was being scaled back to focus on repeat offenders and those engaged in criminal activities.

Wilmot notified members of the Arizona congressional delegation of the change, complaining it would undermine efforts at border control and would cause border patrol agents "to feel betrayed by the very government that they serve."

"This practice undermines everything that we have worked hard to achieve over the years for the citizens of Yuma County," Wilmot wrote.

Others saw the program differently, with the main criticism being it was creating backlogs in federal courts for questionable reasons.

"The program, which mainly targets migrant workers with no criminal history, has caused skyrocketing caseloads in many federal district courts along the border," argued a 2010 policy brief from the Berkeley Law School’s Chief Justice Earl Warren Institute on Race, Ethnicity & Diversity.

The Carson campaign told us that he wasn't singling out a single factor for what caused the drop in Yuma, and that the campaign stood by his statement.

Our ruling

Carson said that Yuma County has been able to reduce illegal immigration by 97 percent, but that the federal programs that allowed them to do that had been "abolished."

Carson didn’t mention the time frame on the reduction in Yuma County -- those numbers dropped from 2005 to 2014, and experts have credited the reduction to several factors, including a U.S. economic recession. Other factors receiving a share of were fencing construction and the number of border agents

As for the federal programs that have been abolished, we found one program involving prosecutions that fit the bill, but it had been scaled back rather than eliminated, and it was, at most, one factor among many that are believed to have led to the drop.

So while Carson has a point that illegal immigration has fallen significantly in Yuma County, he glosses over the time frame and incorrectly credits a program that was scaled back but not abolished. On balance, we rate the claim Mostly False.