A newly-released poll has Pete Buttigieg, the openly gay mayor of South Bend, Indiana, leading among 2020 Democratic presidential candidates in Iowa, the first state to hold a presidential contest.

The Monmouth University poll has Buttigieg in the lead with 22 percentage points among caucus-goers. That's an increase of 16 percent since Monmouth's August poll.

Former Vice President Joe Biden (19%), Massachusetts Senator Elizabeth Warren (18%), and Vermont Senator Bernie Sanders (13%) round out the top four spots. The rest of the Democratic field trails with single digits.

Patrick Murray, director of the Monmouth University Polling Institute, said in releasing the poll that Buttigieg's support is coming from a “wide variety of Iowa Democrats.”

“Buttigieg is emerging as a top pick for a wide variety of Iowa Democrats,” Murray said. “While he has made nominally bigger gains among older caucus-goers, you really can't pigeonhole his support to one particular group. He is doing well with voters regardless of education or ideology.”

Pollsters also found that Buttigieg has the highest approval rating among Democratic presidential hopefuls. Sixty-three percent of caucus-goers said that they approve of Buttigieg, compared to Warren at 46%, Biden at 39%, Minnesota Senator Amy Klobuchar at 36%, and Sanders at 32%.

Buttigieg's campaign has invested heavily in Iowa.