J.J. Koch, who has a high chance of becoming the next sole Republican on the Dallas County Commissioners Court, says blame for the county's declining middle class falls in large part on one group: unauthorized immigrants.

They make up roughly 7 percent of the county, according to the Pew Research Center, but Koch believes they have put an outsize burden on public schools, social services and the economy.

"This shrinking of the middle class won't stop until we end the flow of illegal immigrants into our County," Koch said Thursday in a campaign email to his supporters. "That time-tested formula for achieving the American dream will end in Dallas County if we don't take immediate action to change course and enforce our laws."

Koch, a Dallas attorney, led the Republican primary for northern Dallas County's District 2, which has long leaned Republican. He faces former state District Judge Vickers "Vic" Cunningham in the runoff election May 22. As county commissioner, Koch would not have much power over immigration, besides oversight of the county jail, which already hands over unauthorized immigrants to the federal government.

Some saw Koch's mailer as purely political — trying to capitalize on the widespread concerns about unauthorized immigration that helped propel Donald Trump to the presidency.

"It is disappointing to see this sort of fear-mongering from someone who wants to serve on the Commissioners Court," said Commissioner Elba Garcia, a Mexican immigrant. "County governance is about management — competent administration and prudent stewardship of taxpayers' dollars, not partisan grandstanding."

Koch was weighing in on a new report out this week from the Center for Public Policy Priorities that showed rising poverty and racial inequality in Dallas County. One key statistic: Median household income fell 16 percent since 1999, the report found.

"What has changed since the rise in poverty?" Koch said in the email. "The answer is hidden in their own chart," he said, referring to a graph that showed the county population growing far less white and far more Hispanic over time.

By 2050, Dallas County will have 1.9 million Hispanics, 404,000 whites, 641,500 blacks and 300,000 people of other races, the report said. Koch took issue with the report not differentiating between all Hispanic people and unauthorized immigrants.

Koch said unauthorized immigrants fuel economic woes because they burden public schools with more poor students and non-English speakers. He said such immigrants also accept jobs for lower wages, which leads to salaries falling for other similar jobs. And, he added, those issues lead to more "not just white flight, but middle-class flight" to the suburbs.

"People immediately say, 'You're being racist,' but clearly this has nothing to do with racial origin," Koch said. "It has to do with: a bunch of poor people came over the border and settled here in Dallas."

Dallas attorney J.J. Koch (center) answered questions in an editorial board meeting as former Garland City Council member Stephen Stanley (left) listened and former state District Judge Vickers "Vic" Cunningham took notes in February at The Dallas Morning News. (Vernon Bryant / Staff Photographer)

He added that unauthorized immigrants use social services and resources that would be better spent on native-born people living in poverty.

"If we want to be really honest about it, illegal immigrants are taking away resources that we could use to create a strong, thriving black middle class in Dallas County," Koch said.

In response, Garcia said immigration "is one of the great strengths of our economy in North Texas." The county's unauthorized immigrants work in construction, manufacturing and service industries, and 34 percent are homeowners, she said.

Citing a 2016 study by the Texas Public Policy Foundation, she said unauthorized residents in Texas paid $178 million in property taxes and $1.4 billion in sales taxes in 2010.

"This shows that undocumented residents of Dallas County contribute to the economy of our community with both their labor and their disposable income, as well as being part of our community tax base," Garcia said.

Garcia added that the middle class in Dallas is most hurt by the rise in housing prices, coupled with relatively unchanged wages.

"I do not believe that either of these issues is caused or exacerbated by undocumented immigrants," Garcia said.

Hector Flores, former president of the League of United Latin American Citizens, said immigrants often take jobs that are dangerous, pay little and offer no benefits. U.S. citizens wouldn't work those jobs, he said.

"He's trying to race-bait," Flores said of Koch. "He's trying to duplicate the GOP plan that got our POTUS into office by arousing the darker side of Americans."

In his email, Koch called himself "the only candidate openly committed to enforcing the rule of law"and "the only candidate who understands the magnitude of this issue and has the courage to take it head on."

His opponent, Cunningham, brushed that off as "more big talk from Mr. No Experience."

"As a State Criminal District Judge, I worked with ICE on a regular basis deporting criminal illegal aliens," Cunningham said in an email. "As county commissioner I will fight against sanctuary cities and will always uphold the rule of law, just as I have always done during my 30 year career in criminal justice."