STORM LAKE, Iowa – During the 1960s and 1970s, Richard Krout slaughtered hogs at a now-defunct meat-processing plant where the union label helped him earn more than most teachers. The work was strenuous, but the pay and benefits made it a job many Iowans wanted for themselves and their grown children.

Today, he said, the work is being done more cheaply, mostly by foreign-born workers with low job expectations.

“They'll work as much as you want and under just about any conditions, and they won't ask questions,” he said. He lamented that those meat-packing jobs, once so prized across the Midwest, have deteriorated to the point that few native Iowans want them.

Krout's bitterness reflects a broader concern among many Iowans over the perceived impact of immigration on their state. Those concerns are being felt in the presidential campaign here in America's heartland, especially for Republican hopefuls.

When Iowa Republicans hold their first-in-the-nation caucuses Jan. 3, some say immigration will be a prominent voting issue here for the first time.

Rightly or wrongly, some GOP voters associate the swelling population of foreigners with rising poverty, declining real wages, uninsured drivers operating without valid licenses, swelling school enrollment, declining student performance, rising crime and crowded housing.

“To me, it ties in with terrorism; it's security; it's a political issue; it's health care,” said Sallie Vorrie of Fort Dodge, who came to a recent campaign stop to press former Sen. Fred Thompson of Tennessee to crack down on illegal immigrants. “I think a lot of these people are going to our hospitals for health care. We're paying. If we didn't have to pay for these freeloaders, we'd be better off. And a lot of them are going on welfare. And I am sick of it.”

Voter angst in Iowa over immigration has been especially hard on Arizona Sen. John McCain, one of the leading sponsors of legislation to provide legal status to millions of immigrants. That measure failed in Congress amid protests from across the country.

“McCain is simply not competitive here, and to a great extent that's because of the immigration issue,” said politics professor Dennis Goldford at Drake University in Des Moines.

Meanwhile, Colorado Rep. Tom Tancredo has developed a core of supporters for a candidacy based almost entirely on his hard-line stance against illegal immigration.

The Republican front-runner in Iowa, former Gov. Mitt Romney of Massachusetts, criticized the McCain-sponsored measure as amnesty and declared his determination to stop illegal immigration. Romney has chided Rudy Giuliani for his record when he was mayor of New York, saying Giuliani's public welcome of illegal immigrants encouraged more people to enter illegally.

Giuliani has responded with a vow to “end illegal immigration.”

The issue holds far less voltage for the Democratic candidates, all of whom favor giving legal status to many of the nation's estimated 12 million illegal immigrants.

“The Democrats see it as a humanitarian as well as a legal issue, and they want to find a solution on that basis,” Goldford said.

Storm Lake, a bucolic college town with a 3,200-acre natural lake surrounded by city parks and homes, began receiving a trickle of Laotian refugees in the mid-1980s. That was followed by a slightly larger flow of Mexican Mennonites in the early 1990s. In the mid-1990s, a larger influx of non-Mennonite Mexican workers began, and it has continued to grow.

All three waves directly resulted from recruitment efforts by the largest meat-processing plant in Storm Lake, now owned by Tyson, according to a study done by Mark Grey of the anthropology department at the University of Northern Iowa.

While the foreign-born work force has helped Tyson's bottom line, Grey found that the influx of the workers and their families to Storm Lake correlated with an increase in poverty, crime, local public health care costs, school expenditures and a range of other adverse economic impacts on the community.

Numbers are part of the story, even in a state where 91 percent of the population is white. The U.S. Census Bureau reported a 39 percent increase in the state's Latino population between 2000 and 2006. The state's 114,700 Latinos tend to cluster around meat-processing plants in towns such as Storm Lake, Denison, Perry and Marshalltown.

While the numbers might seem small, the reactions are intense.

“They're angry about global economic changes, but I don't know how many people see that,” said Storm Lake Police Chief Mark Prosser. “What they see are the immigrants. They can't understand them in the aisles of the store. They see property maintenance issues. There's a lot of folks who are scared.”

Sara Monroy-Huddleston said she believes the fears and concerns about the influx of immigrants are overblown. A native Mexican, Monroy-Huddleston thought her election to the City Council here four years ago was a watershed moment in which residents were saying to immigrants, “We want you to be part of the community.”

But acceptance only goes so far.

She believes the fundamental problem is a cultural chasm between those born into the middle-class American heartland and immigrants, most of whom are from Mexico's peasant class.

“Some people feel like the people come into their homes and it's like they're putting their feet up on the furniture,” said Monroy-Huddleston.

In an old farmhouse along an unpaved road 30 miles south of Storm Lake, the congressman who represents western Iowa sat at his kitchen table and worried that immigration is shaping “a Third World America.”

Steve King, the top Republican on the House immigration subcommittee, has made immigration enforcement the centerpiece of his campaign. He doubts that Iowa's highly regarded public school system can deal with the challenge of helping the children of immigrants find a way to the middle class.

“There's a commitment to education that comes with a culture,” he said. “But you don't see that in large numbers among those coming across the southern border.”