Democratic candidates are close behind Joe Biden in a new Iowa poll

Democratic presidential candidate Joe Biden is leading the Democratic field in the crucial early caucus state of Iowa, according to a new poll.

Closely trailing Biden are Sens. Bernie Sanders and Elizabeth Warren, with South Bend, Indiana Mayor Pete Buttigieg not far behind.

Biden has come under intense scrutiny from other 2020 Democrats in recent days, prompting him to reverse his position on federal funding for abortion.

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Democratic presidential candidate and former Vice President Joe Biden is at the top of the field in Iowa, the first state in which voting takes place in the primary race next year, according to a new poll .

But as Biden has faced heavy criticism over his stance on abortion, for which he reversed a decades-long held position, the race appears to be tightening as more Democrats climb in the polls.

Read more: Joe Biden is running for president in 2020. Here's everything we know about the candidate and how he stacks up against the competition.

In a poll released Saturday by CNN, Des Moines Register, and Mediacom, Biden edges out the rest of the Democratic field with 24% support. Behind Biden are Vermont Sen. Bernie Sanders with 16%, Massachusetts Sen. Elizabeth Warren with 15%, and South Bend, Indiana Mayor Pete Buttigieg with 14%.

None of the other candidates crack double digit polling, including California Sen. Kamala Harris, who garners just 7% in the new poll conducted by Selzer and Co.

While Biden leads the Democratic field in most polls, the CNN poll provides insight to what could become a problem for the campaign: lack of enthusiasm for his candidacy compared to others in the 24-person field.

Just 29% of Biden's supporters in the poll characterized themselves as “extremely enthusiastic” about his campaign, compared to 43% for Sanders and Warren, and an average of 39% for the rest of the candidates in the race.

In a caucus system like Iowa's, enthusiasm is a key factor for candidates looking to court supporters and earn a large chunk of delegates.

Read more: There are 2 different ways for states to choose presidential nominees — and there are some major differences between them

Biden reversed his position of opposing federal funding for abortion earlier this week, a stance he had held for several decades in public service. The Democratic field had largely avoided criticizing one another until this past week when many of the two dozen candidates actively called out Biden, who then flipped his position.

In addition to abortion, long shot candidate and Massachusetts Rep. Seth Moulton called out Biden for voting in favor of authorizing the Iraq War.

“Bravo to [Biden] for doing the right thing and reversing his longstanding support for the Hyde Amendment,” Moulton, who served in Iraq, wrote on Twitter. “It takes courage to admit when you're wrong, especially when those decisions affect millions of people. Now do the Iraq War.”

Whether Biden will continue to lead the 2020 field is up in the air, especially as the primary debate season gets underway later this month.