IOWA - Donald Trump has a huge and expanded lead over his rivals for the Republican presidential nomination in a new poll in Iowa, the state that kicks off the party's nominating contest on Jan 15.

The former president has 51 per cent first-choice support from people likely to take part in the Iowa caucuses in January, according to a NBC News/Des Moines Register/Mediacom poll released on Dec 11, up from 43 per cent in the same poll conducted in October.

Florida Governor Ron DeSantis has 19 per cent first-choice support in the poll - up from 16 per cent in October - while former United Nations Ambassador Nikki Haley is at 16 per cent, unchanged since the last poll.

Iowa uses a different system to pick presidential candidates than most other states where a traditional ballot is employed. Voters in Iowa - or caucus goers - will gather for several hours in thousands of locations on Jan. 15 to debate the candidates before ranking them. Polling Iowans' first-choice preference is the best indicator of candidates' support.

Despite myriad legal problems - he faces multiple criminal charges over his role in the deadly Jan 6, 2021 riot at the US Capitol, hush money payments to a porn star, and stolen classified documents - Trump is currently the runaway frontrunner to secure the Republican presidential nomination to face Democratic President Joe Biden in next November's election, a likely re-match of the 2020 contest.

J. Ann Selzer, a veteran Iowa pollster who conducted the survey, called Trump's lead in Iowa "commanding".

Trump's lead in Iowa is fueled by majorities of evangelical and first-time likely caucus goers, and by nearly three-quarters of Republicans who believe Trump can beat Biden next year, according to the poll.

Trump is also enjoying commanding leads over his Republican rivals in national polls and in New Hampshire, the second state to vote in the Republican nominating contest on Jan 23. REUTERS