Pete Buttigieg has surged to third place in a new poll of Democratic presidential candidates, ahead of Kamala Harris, Elizabeth Warren and Beto'Rourke.
The 37-year-old mayor of South Bend, Indiana, won the backing of 11% of likely Iowa Democratic caucus voters in an Emerson poll released on Sunday.
Joe Biden had 25% support, with Bernie Sanders in second place with 24%. But the performance of Buttigieg, who has impressed in a series of TV appearances, is likely to serve as a warning to his better-known rivals.
Buttigieg had 0% support in Emerson's January poll, which was conducted just after he formed an exploratory committee.
He has not yet formally declared he is running to take on Donald Trump next year but he has been widely praised for his performance in a CNN town hall and in high-profile interviews. He has met the 65,000-donor threshold that qualifies him to take part in the Democratic debates.
Harris, a senator from California, had 10% support in the Emerson poll - which had a margin error of +/- 6.2% - while Warren of Massachusetts was in fourth place with 9%.
Beto O'Rourke, the former congressman from Texas who has captured the attention of the public and the media with a combination of relentless charm and non-committal policy positions, was backed by 5% of likely voters.
Buttigieg supports the Green New Deal proposal, a series of climate change reforms backed by progressive Democrats, and has said he is in favor of single-payer healthcare, an issue fast becoming a litmus test for Democratic candidates.
Were he elected, Buttigieg would be the first openly gay president. In South Carolina on Saturday, he told voters his marriage existed "by the grace of a single vote on the US supreme court", and said it had brought him closer to God.