The snow and fairy lights make Main Street resemble a scene from It’s a Wonderful Life, with only a glimpse of a Mexican flag in the grocer’s window or a handwritten sign in Spanish indicating that this is different from dozens of other mid-Western towns.

But on the outskirts of Marshalltown, the grey windowless bulk of the Swift & Co meat plant looms out of the fog like a battleship. And it is there that workers hurry away from the gates, waving away questions with a polite “No hablo inglés”.

In December last year US immigration agents raided the factory at dawn, divided the workers into two groups – US citizens on one side, Mexicans on the other – and detained 99 people for lacking legal documentation. Children arrived home to find that their parents were gone, others were left crying at school because there was no one to pick them up.

This Christmas, fears of deportation among the 7,000-strong Hispanic community have been exacerbated by a presidential election in which illegal immigration has emerged unexpectedly as the principal concern for Republican voters in Iowa. In this crucial state, where the nomination process begins on January 3, candidates for the White House have been loudly trumpeting – or tripping up over – the immigration issue.

Although Iowa remains overwhelmingly white – with Latinos accounting for less than 3 per cent of its population – the arrival of immigrants in places such as Marshalltown, where Hispanics number 7,000 and represent a proportion of perhaps 25 per cent, has caused some resentment.

Bobbie Sullivan, 58, waiting for her boyfriend outside Swift & Co, describes a feeling of being “overwhelmed” in her church, where three quarters of the congregation are Spanish speakers. “It hurts when poor people here are without jobs to see all the Hispanics there,” she says. “And they get all the overtime there is to be had, ’cos they work so hard.”

Swift & Co denied The Times access to the plant where many of the 2,000-plus employed there undoubtedly have tough jobs. Notices in the security office refer to rooms dedicated to a “blood trough” or “old green meats” and, in a country built by immigrants, there is still much admiration expressed for the can-do attitude of Hispanic labour. This, however, has become tempered by a growing sense of insecurity fed by a constant diet of reports about America’s “broken borders” and its 12 million-strong army of illegal immigrants.

The rapidly rising salience of the issue in presidential politics has taken some candidates by surprise. John McCain was almost destroyed this summer for backing, with President Bush, legal rights for undocumented worker immigrants. Other Republicans have largely fallen into line with a new orthodoxy with Rudy Giuliani, Mike Huckabee and Mitt Romney stampeding to sound the toughest. Karl Rove, who masterminded Mr Bush’s two presidential victories, worries that the Republicans are cutting themselves off from pro-family, socially conservative Latino voters, the fastest-growing section of the US electorate. But Hillary Clinton’s recent fumbling of a question on whether illegal immigrants should be allowed driving licences illustrates why Democratic candidates are also viewing the subject nervously. Some strategists fear it has potential to be another "wedge issue" driving working class Democrats away from the party just as abortion and gay rights did before.

For Mary Ibarra, who grew up in Iowa as the daughter of a Mexican immigrant and an American Indian mother, it has all become too much. Her partner, Mario, was deported for not having papers, and she has been left struggling to raise four children and hold down her job at the plant. She plans to move her family to Mexico. “If they don’t want him here, that is their mistake,” she says.

Question that tops the polls

— There were 34.2 million immigrants in the US in 2004; 18.3 million came from Latin America, 8.7 million from Asia and 4.7 million from Europe

— There are an estimated 12 million illegal immigrants across the US, 1 in 20 of the working population

— Illegal immigrants contributed $8.5 billion in social security and Medicare funds last year, and almost $50 billion in federal taxes from 1996 to 2003

— In 1970 Iowa published a treatise, Iowa: The Home for Immigrants – its purpose to “induce thousands to find homes within the borders of Iowa”

— Schools in Storm Lake, northwest Iowa (the city with the highest percentage of Hispanic people in Iowa) are 49 per cent Hispanic, 10 per cent Asian and 4 per cent African-American

— In 2000, when Governor Tom Vilsack announced immigrant recruitment, a Des Moines Register poll indicated that 58 per cent of Iowans opposed encouraging immigration

— In 2006, President Bush proposed an overhaul of US immigration laws. It was opposed by Republicans, who backed its tougher security measures but opposed efforts to grant citizenship to illegal immigrants

Sources: uiowa.edu; nh.gov; census.gov; National Immigration Law Centre; Times archives

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