PLAINFIELD, Iowa — As presidential hopeful Scott Walker toured a farm in this tiny town where he lived as a child, he was confronted by an undocumented worker from Mexico who is living in Wisconsin and demanded to know why Walker does not support President Obama's plan to give temporary status to some undocumented workers, including parents of children who were born in the United States.

"We're a nation of laws," Walker, the Republican governor of Wisconsin, repeatedly told Jose Flores, 38, who was joined by two of his four children, Luis, 7, and Leslie, 13, who had tears rolling down her cheeks throughout the exchange. Flores, who lives in Waukesha and works for a medical supply factory, said he and his wife live in fear of being deported and separated from their children, who he said were all born in the United States.

"My point," Walker said, "is that you have to follow the law, follow the process."

Immigration has been a weak area for Walker, who announced his presidential campaign last week in the same town where the Flores family lives. Although he used to support granting amnesty to some of the 11 million immigrants who are in the country illegally, Walker now says his position has changed. He said that those living here need to leave and reenter legally, prompting some critics to accuse him of flip-flopping. Walker also has suggested curtailing legal immigration during difficult economic times.

Even though immigration has often dominated this presidential contest, Walker did not mention it in his announcement speech or his first couple of campaign stops, including a breakfast at a Harley-Davidson dealership in North Charleston, S.C. Afterward, Walker was confronted by a man who shouted, "What about the border?" At the next campaign stop, a barbecue joint in Lexington, Walker added immigration to his stump speech and continued to talk about the issue — nearly always receiving loud, supportive cheers.

Wisconsin Gov. Scott Walker is a Republican contender for president. Here's his take on border security, tax reform and same-sex marriage, in his own words. (Sarah Parnass/The Washington Post)

The campaign stop in Plainfield was a joyful homecoming for Walker, who lived in this town of about 400 for seven years as a child in the 1970s. Residents brought lawn chairs to a large machine shed to meet the local boy who is now running for president. The hosts were Janice and Charlie Dietz, who decades ago interviewed Walker's father for the pastor position at their church and then became close family friends. Walker's parents and third-grade teacher were in attendance, too. Walker spoke fondly of buying circus peanut candy at the corner store, swimming in a neighbor's pool and collecting money for a state flag for the city hall. He posed for photos with corn and cows and gushed about Midwestern values.

It was a childhood quite different from that of Leslie and Luis Flores, who said they worry about their parents being deported. Leslie Flores, who is in middle school, said her mother was unable to travel to Mexico to see her father before he recently died. The teenager said that she has seen "so many families" torn apart by deportation.

The Flores family stood out in the white crowd, a reminder that Iowa towns such as this one and others where Walker has campaigned are not always fully representative of the nation's diversity. At first, Walker told the family that he did not have time to talk to them, as he had an interview with Fox News Channel. But the Flores family waited by his campaign bus and approached him again, an exchange that was captured by reporters and three immigration activists, one of whom drove the family to Iowa.

It was an opportunity for Walker to demonstrate how he calmly fights back against challenges from activists. He was forceful as he told the Flores family that immigrants must follow the rules, but he added, "I completely sympathize with the situation you're all in and others are in."

One of the activists, Sam Freeman of Wisconsin's Voces de la Frontera, cut the governor off and shouted, "So that's why you want to separate their family?"

Walker curtly said that he wanted to talk only with the family and that their plight is the reason the United States must go forward with "putting in place a logical system." To address illegal immigration , Walker said, the nation needs to secure the border and enforce its laws before it can focus on other issues. An immigration system cannot come at the cost of American workers and their wages, he added.

"The president had years to deal with this throughout the legitimate legislative process," Walker said. "He had his own party in charge for the first two years … he was in office."

Flores listened intently to Walker and then said, "Now it's my turn."

In November, Obama announced that he would use his executive authority to shield 5 million illegal immigrants from deportation and allow them to legally work in this country. This become known as Deferred Action for Parents of Americans and Lawful Permanent Residents, or DAPA. Twenty-six states, including Wisconsin, sued, calling the executive action unconstitutional. Such legal action has halted the program.

Flores repeatedly asked Walker why he tried to block DAPA. Walker told him that he is a governor and not part of the federal government or the legal system. Flores said thousands of Wisconsin families could have benefited.

"When are you guys going to fix the immigration system?" Flores said. "When are you guys going to take the time to fix immigration reform? So we've got to be deported?"

Walker stayed on message, listing his immigration talking points and criticizing Obama for not fixing the system. He also said that he supported the lawsuit Wisconsin filed to stop Obama's executive action.

"No man or woman is above the law in this country," Walker said. "That's the beauty of America."

Then Luis Flores jumped in: "Do you want me, like, to come home … come from school and my dad get deported?"

"No, that's not what I'm talking about," Walker said. "You mentioned Waukesha. I've got two nieces who go to school there as well. … I appreciate kids like you and kids like them, so that's not what my point is. My point is that in America, nobody is above the law."