WASHINGTON (Reuters) -Former U.S. President Donald Trump maintains a commanding lead over his Republican rivals in Iowa less than three months before the state kicks off the Republican presidential nominating contest, with Nikki Haley and Ron DeSantis tied for second place, an NBC News poll released on Monday showed.

The survey, conducted with the Des Moines Register and Mediacom last week, found Trump with a nearly 30-percentage-point advantage over the former U.S. ambassador to the United Nations and the Florida governor ahead of the Jan. 15 caucuses in the Midwestern state.

Trump is showing strength in Iowa despite considerable legal challenges. The former Republican president faces four criminal and three civil trials, some related to his attempts to overturn his 2020 loss to Democrat Joe Biden. Still, 65% of those surveyed said he could win the November 2024 contest versus Biden, who is seeking another term.

"He’s still the dominant player in the field, and his standing has in fact improved from August," said J. Ann Selzer, who conducted the poll.

Among the 404 likely Iowa caucus-goers surveyed Oct. 22-26, 43% chose Trump as their first-choice candidate, while 16% picked Haley and another 16% selected DeSantis, according to the poll, which has a margin of error of plus or minus 4.9 percentage points.

The poll is a worrisome sign for DeSantis, who has spent more time campaigning in Iowa and has devoted the most resources to the state of any candidate, and an encouraging one for Haley, who has gained momentum after two solid debate performances.

Trump's 27-percentage-point advantage is up from August, when the poll showed a 23-percentage-point lead over DeSantis. Many Republicans have said they believe the charges facing Trump are politically motivated.

The poll was conducted before Trump's former vice president, Mike Pence, dropped out of the race over the weekend.

(Writing by Susan Heavey and James Oliphant; Editing by Chizu Nomiyama and Jonathan Oatis)