"Perched on the northern bank of the Rio Grande opposite a giant fluttering Mexican flag 300 metres across the border, Universal Guns Ammo is hardly the best vantage point to observe the Democratic ­presidential race.

But for the first time in years, Hart and Delila Raesch, a German-Mexican couple who own the gun store from which they often spot illegal immigrants emerging from the river, say they feel in the thick of the electoral battle.

"I can’t remember the last time people talked so much about an election,” said Mrs Raesch.

Next Tuesday the 300,000 or so citizens of Laredo will play an important role in choosing the Democratic nominee when the border town goes to the polls with the rest of Texas in a must-win primary for Hillary ­Clinton.

Having lost the last 11 contests to her rival Barack Obama and watched her support begin to fray among the once rock-solid base of blue collar, elderly and women voters, Mrs Clinton is banking on Latinos – her last great pool of loyal voters – to come out in droves.

Making up a third of the Texas population and 97 per cent in Laredo, they will have a critical impact on the outcome. In California and most other states, Latinos broke two-to-one in Mrs Clinton’s favour on Super ­Tuesday.

In Laredo people remember the Clintons from 1991 when they wooed local officials to back Bill’s then hopeless-seeming presidential bid. Mrs Clinton is also remembered by some of the older generation as a young activist who spent three months in Texas in 1972 helping to register Latinos to vote.

That, and the fact that Laredo remains heavily working class in spite of its long-running boom that began with Mr Clinton’s conclusion of the North American Free Trade Agreement in 1994, ought to make it landslide territory for Mrs Clinton. But few local officials have endorsed her or Mr Obama, preferring to wait and see who prevails.

There is also an intensity that gives this race a novel quality. “I have lived here since 1968 and never seen energy like this,” says Mr Raesch.

“Three months ago I would have predicted a landslide for Hillary. Now it is not so clear.”

The picture looks clearer inside Rita Maya, a Mexican-American café in the city of San Antonio, 155 miles north of Laredo. Owned by Caterina Vesasquez, the daughter of the late William Velasquez, a local legend for having pioneered the Latino civil rights movement, the place is filled with young Obama supporters.

Ms Velasquez, who maintains a piggy bank that asks customers to donate “change for change” in an echo of Mr Obama’s chief mantra, says that young Latinos, particularly educated ones, are breaking for Mr Obama.

If her observations hold, that is bad news for Mrs Clinton because African-American Texans of all ages will vote for Mr Obama and whites are likely to be split. And if she loses either Texas or Ohio, which also votes on Tuesday, her campaign could dissolve.

To win Texas Mrs Clinton needs a high turnout in Latino-dominated districts since under the state’s unique system delegates are allocated on the basis of turnout in the previous election, when black districts voted in much higher numbers than Hispanic ones. This time everyone anticipates high Latino participation but with a marked demographic split.

“Almost as a rule, young Latinos are for Obama and their parents are for Hillary,” says Ms Velasquez, who is hosting an “Artists for Obama” session, one of whom plays Bob Dylan’s “The times they are a’changing”. “A lot of us are all tired of the same-old same-old.”

In contrast to expectations a few months ago, the controversy over illegal immigration is playing almost no role. That is partly because the Republicans are set to nominate John McCain who, alone among his rivals, took a moderate stance towards America’s 14m “undocumented workers”.

It is also because Mrs Clinton and Mr Obama want to avoid pledges that could embarrass them later on. The start of Mrs Clinton’s declining poll numbers can be traced to an equivocal – and therefore cynical (said critics) – response to a question about whether illegal immigrants should be able to get drivers licenses in a televised debate last October.

Both are pitching Spanish-language TV spots that focus on healthcare, the economy and the Iraq war.

A third of Texan Latinos say they have a friend or relative on the frontline in Iraq. In contrast, the US-Mexico fence, which has been approved by Congress but remains largely unconstructed, is only a live issue in towns such as Laredo.

“My house-keeper was recently flagged down by the police and deported,” says a Laredo bank manager who asked for her name to be withheld. “When I returned home that afternoon she was already back in the kitchen.”" (Edward Luce, The Financial Times, February 28, 2008)