Des Moines, Iowa - Donald Trump dominated his closest Republican presidential primary competitor, Florida Governor Ron DeSantis , in a survey of Iowa voters published Monday, the latest signal of strength for the former president.

The poll, published by the local newspaper The Des Moines Register, found Trump thrashing DeSantis by 23 percentage points in Iowa – a gap smaller than his national lead, but still formidable.

For DeSantis or any other dark horse seeking to dethrone Trump in the GOP White House race, Iowa could be a critical proving ground.

Iowa, which has an evangelical-leaning electorate, has been described as a relatively challenging primary state for Trump, whose bid to return to the White House has been shadowed by four indictments this year.

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Trump's poll numbers have strengthened in recent months as the charges have piled up.

DeSantis, long seen as Trump's strongest rival, has been bedeviled by budget troubles. His poll numbers said through the spring and into the summer, and he replaced his campaign manager two weeks ago.

Republican Iowa voters are slated to head for their first-in-the-nation caucus next January.

The first Republican presidential debate this cycle is scheduled for Wednesday on Fox News. Trump has said he will not attend, but his former vice president-turned-rival Mike Pence has said he thinks the front-runner might still show.

The Des Moines Register poll, which was also sponsored by NBC News and US cable television provider Mediacom, was conducted by phone last week, before and after Trump's election interference indictment in Georgia, the newspaper said. The Selzer & Co. pollster surveyed 406 likely Iowa caucus-goers, according to the Register.

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In the poll, Trump finished with 42% support, DeSantis nabbed 19%, Senator Tim Scott of South Carolina notched 9%, and South Carolina's former governor Nikki Haley scored 6%.

Pence picked up 6%, and Chris Christie, the former New Jersey governor, was the first choice of 5% of voters. Vivek Ramaswamy, a biotech bigwig, picked up 4%.

Nationally, Trump led DeSantis by about 39 percentage points on Monday, according to an average of polls by FiveThirtyEight, a survey aggregator. Ramaswamy was in third nationally, about 46 points behind Trump, according to FiveThirtyEight.