Top 4 Democrats statistically neck and neck in Iowa presidential poll

By the numbers: Sanders is the top choice for president for 20% of likely attendees to the Democratic caucus, the poll shows. Warren stands in second place at 17% and Buttigieg takes third at 16%, while Joe Biden stands at 15%.

Methodology: The latest poll tallied 701 likely Democratic caucus-goers from Jan. 2-8. The poll's margin of error is -/+ 3.7 percentage points.

• Due to the poll's margin of error, all four top candidates are in a statistical dead heat.

Be smart: Sanders clawed back 5 percentage points from the November poll, when Buttigieg was the first choice among 25 percent of likely caucus goers. Warren came in first among 16 percent of those polled, while Biden and Sanders were each the favorite of 15 percent at the time.

Yes, but: Sanders beat his competitors in Q4 fundraising, raking in $34.5 million — while Buttigieg followed at $24.7 million.

• Sanders' "anti-establishment message hasn’t changed for 50 years, and it resonates with working-class voters and young people who agree the system is corrupt and it will take a revolution to fix it," the New York Times' Sydney Ember wrote in December.

Go deeper: Bernie Sanders is the dominant Democrat of the Trump era

Editor's note: This piece has been updated to show that Sanders has gained momentum in the January poll.