Des Moines, Iowa – One month from now, Iowa kicks off the US 2024 primary season, and Donald Trump will discover whether he has an insurmountable lead for the Republican presidential nomination, or opponents can spring a surprise.

Four criminal indictments are pending against Trump, putting the former president at risk of going to prison.

Still, he has one of the biggest poll advantages in modern times over Republican rivals at this point in a campaign.

While they all are vying to run in next November's election as the party seeks to unseat Democratic President Joe Biden, Trump is dominating the race so far.

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"We're going to make America great again," Trump promises at his rallies, echoing the slogan that catapulted him to power in 2016.

But as past US elections have shown, polls this far ahead of the vote should be viewed with caution.

The real verdict comes in the intraparty nominating contests of various states, starting with the Iowa caucuses on January 15, when Trump will hear from voters for the first time since leaving the White House.

As tradition dictates, voters in the rural state will open the primary season, as they have done since 1972, gathering in places like school gyms and fire stations to poll on their preferences at individual precinct meetings known as caucuses.

In Iowa as elsewhere, Trump still has a loyal base that brushes aside his legal troubles.

"I don't even understand what the crime is," said Adam Miller, a 61-year-old farmer and Trump supporter whom AFP met in Makoqueta, a town in eastern Iowa near the Mississippi River.

"I mean, if he's accused of murder or bribery... then that would change my mind."

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On January 15 at 7 PM, this dark-haired, bespectacled man will gather with residents of his community, a three-hour drive from Chicago, to fill out a ballot in the name of the billionaire, accused, among other things, of election interference and mishandling classified information.

On that night, six other Republicans will be in the running to block Trump's path. Only two still seem to have a chance.

They include Florida Governor Ron DeSantis, a conservative with hard-right positions on immigration and LGBT+ rights who has staked everything on Iowa, crisscrossing the state's 99 counties in the space of a few months.

The 45-year-old can also count on the patronage of Iowa Governor Kim Reynolds, who has endorsed him. While Reynolds remains popular among Republicans, Trump savaged her after she backed DeSantis, branding her "America's most unpopular governor."

Support for DeSantis, a former naval officer, appears to have plummeted in recent months, which some blame on his occasional wooden demeanor and lack of charisma.

Then there's former UN ambassador Nikki Haley, the new darling of the American right. The 51-year-old former governor of South Carolina has cut a different path with a more moderate stance on reproductive rights, aware that her party has suffered several electoral setbacks since the Supreme Court last year overturned the constitutional right to abortion.

Throughout the campaign, both Haley and DeSantis have employed fancy footwork to avoid direct attacks on Trump, for fear of offending his supporters.

Both hover around 12 percent in the polls, a far cry from the former president's 60 percent.

But observers are not ruling out the possibility either of them could spring a surprise and nibble away at the tempestuous Republican's dizzying lead.

"Anything less than a huge victory means that Trump will look more vulnerable in the GOP nominating contest than observers, donors, and voters expected," Brown University political scientist Wendy Schiller told AFP.

After Iowa, the electoral spotlight turns to New Hampshire, then to the casino state of Nevada, and South Carolina at the end of February.

By June, all 50 states will allocate their delegate quotas to candidates for July's Republican National Convention, which will nominate the party's flagbearer for the election.

On the Democratic side, barring a huge surprise, incumbent Biden will be nominated in August at the party's convention in Chicago.

This will occur despite repeated criticism about his age, 81.

Two candidates, congressman Dean Phillips and best-selling author Marianne Williamson, are challenging Biden for the Democratic nomination, but their chances are slim.