Two government outsiders have emerged as the top choices for the next United States president among Republican voters in Iowa, a state where caucuses provide an early indication of which presidential candidates are likely to secure the nominations of their political parties.

Controversial real estate mogul Donald Trump and retired neurosurgeon Ben Carson were tied for the top spot in a presidential preference survey conducted last week among Iowa residents by Monmouth University in New Jersey. The survey results were released on Monday.

Both Trump and Carson got 23 percent of the votes of Republican caucus-goers.

"Not surprisingly, given the top two contenders in the poll, most Iowa Republicans prefer someone without a traditional political pedigree. At this early stage, though, the vast majority of voters say their eventual support could go to one of several other candidates in spite of their current preference," Monmouth University said in the statement announcing the poll results.

Businesswoman Carly Fiorina was a distant third, securing the nod of 10 percent of the Republican respondents.

Taking the fourth and fifth places were Senator Ted Cruz of Texas (9 percent) and Wisconsin Gov. Scott Walker (7 percent).

Patrick Murray, director of the independent Monmouth University Polling Institute, explained that this recent survey showed major changes in the preference of Republican voters from Iowa.

"These results mark a significant shakeup in the leaderboard from Monmouth's Iowa poll taken before the first debate. Carson and, to a lesser extent, Fiorina have surged, while Walker has faded into the background," Murray said.

Walker was the Republican frontrunner in mid-July, garnering 22 percent from the respondents. During the same period, Trump was only in second place with 13 percent, while Carson came in third with just 8 percent.

Fiorina, for her part, was in fourth place, with only 3 percent of Republican voters in Iowa expressing inclination to vote for her.