Former U.S. President Donald Trump holds a commanding lead over his Republican rivals in the state of Iowa, where the party's presidential nominating contest begins in January, according to an opinion poll released on Monday.

The Des Moines Register/NBC News/Mediacom survey of likely Iowa Republican caucusgoers shows Trump has the backing of 42%, with Florida Governor Ron DeSantis at 19% and U.S. Senator Tim Scott in third place with 9%.

Other Republican candidates in the crowded field aiming to take on Democratic President Joe Biden in the November 2024 election registered in lower single-digit numbers.

Even so, J. Ann Selzer, the veteran Iowa pollster whose firm conducted the survey, said the race is not settled and might be "closer than it may first seem."

A majority -- or 52% -- said they had a first choice for president but could still be persuaded to support a different candidate, while 40% said their minds were made up.

Among Trump supporters, however, 66% said their vote was set, while 34% said they could be persuaded to change their minds.

Trump's four indictments showed little signs of deterring his supporters. The poll found 65% of likely Republican caucusgoers didn't think Trump had committed serious crimes, compared with the 26% who believed he had.

The poll was conducted Aug. 13-17, coinciding with news on Aug. 14 that a Georgia grand jury had issued an indictment accusing him of efforts to overturn his 2020 election loss to Biden.

The survey came ahead of Wednesday's first Republican primary debate, which Trump has said he will skip, citing his large lead in polls.

A national CBS poll on Sunday showed Trump was the preferred candidate for 62% of Republican voters, with DeSantis trailing behind at 16%.

(Reporting by David Ljunggren; Editing by Colleen Jenkins and Jonathan Oatis)