The new poll , conducted for the Democratic group Focus on Rural America by party pollster David Binder, found Buttigieg leading the field with 19 percent of the vote. Sanders trailed with 17 percent of the vote, a statistically insignificant disadvantage.

Both gained 3 points since the last Focus on Rural America poll, conducted in early January.

Warren is the top second choice among voters, taking 20 percent and suggesting she may have the strongest upside potential. Seventeen percent each said Biden and Klobuchar were their second choices, and 13 percent said Sanders would be number two on their list if their chosen candidate is not viable. Buttigieg clocked in fifth, at 10 percent.

The race remains in flux even hours before Iowans head to the caucuses. Only 51 percent of Iowa voters said they were completely certain to stick with their chosen candidates.

“If anyone tells you they know what’s going to happen tonight, they’re making it up,” said Jeff Link, the co-founder of the rural group.

Buttigieg, who has stumped at a frenetic pace across Iowa in recent months, has the highest favorable rating among state Democratic voters. Sixty-nine percent said they see him favorably, just above the 68 percent who said the same about Warren. More than 6 in 10 Iowa Democrats see Biden (62 percent), Klobuchar (63 percent) and Sanders (64 percent) favorably.

The least-favorably viewed Democratic presidential candidate, the poll found, is the one who is not competing for Iowa’s votes. Just 30 percent of Iowa Democrats said they had a favorable impression of former New York City Mayor Mike Bloomberg, who has poured millions into television ads in every state except Iowa. Fifty percent said they see Bloomberg unfavorably.

The poll, conducted Jan. 28-30, surveyed 300 likely caucusgoers and reports a margin of error of plus or minus 5.7 percentage points. That high margin means all four of the top contenders have a realistic shot at winning the caucuses.

The high number of undecided and potentially persuadable voters, coupled with the realignment allowed after a first round of voting, means the actual winner is likely to finish with somewhere north of 30 percent of the delegate vote, Link said.