Three candidates who garnered 3 percent because of rounding are tied for sixth place: Hawaii Rep. Tulsi Gabbard, California Sen. Kamala Harris and Minnesota Sen. Amy Klobuchar. Still, 29 percent of caucus-goers say they remain undecided.

The latest Iowa poll was conducted in the days after the fourth Democratic debate, during which Buttigieg adopted a more aggressive posture and accused Warren of equivocating on the cost of her Medicare For All proposal.

In recent weeks, Buttigieg has sought to establish himself as a pragmatic alternative to primary voters unmoved by Warren's brand of progressive populism and reluctant to embrace the more moderate Biden, whose standing in public polling has begun to diminish.

Buttigieg has also maintained a formidable fundraising operation, raking in $19.1 million in the three months ending in September, the third-largest amount raised by a Democratic candidate in the third quarter of this year— behind Sanders with $25 million and Warren with $24.6 million.

Buttigieg’s top-tier finish in Monday's survey represents a marked improvement from his performance in an earlier Suffolk/USA TODAY poll conducted following the first Democratic debate in late June.

In that summer survey of likely Democratic caucus-goers, Biden led the field with 24 percent, followed by Harris at 16 percent, Warren at 13 percent, Sanders at 9 percent and Buttigieg at 6 percent.

The Suffolk University/USA TODAY poll was conducted Oct. 16-18, surveying 500 likely Democratic caucus-goers. The margin of sampling error is plus or minus 4.4 percentage points.