(CNN) Democratic presidential candidate Joe Biden churned through his campaign donations during the last three months of 2019, leaving the former vice president with a little less than $9 million to spend ahead of the first nominating contests of the 2020 race, new filings late Friday show.

That puts him in a potentially precarious financial position.

Another contender, Sen. Elizabeth Warren of Massachusetts , had $13.7 million remaining in her campaign account at the start of the new year, and former South Bend, Indiana, Mayor Pete Buttigieg had $14.5 million banked.

The news comes just days before Monday's first-in-the-nation caucuses in Iowa , a state Biden has barnstormed this week in the hopes of a strong result that could boost donor enthusiasm and fuel his momentum through the early contests.

South Carolina , considered one of Biden's strongest early-voting states, does not hold its primary until February 29. Days later, candidates face 14 Super Tuesday contests.

Biden and Sanders are at the front of the field for the Democratic national primary, a new CNN Poll of Polls shows. But Biden -- unlike Sanders and Warren -- does not have a vast base of small-dollar donors to fuel his campaign.

Biden received just 38% of his fourth-quarter donations in amounts of $200 or less, the new filings show. By contrast, more than half of Sanders' money came in small amounts, giving him access to supporters who can donate repeatedly before hitting contribution limits.

One sign of financial strain in Biden's camp emerged in recent weeks as it canceled some of the advertising he had planned in New Hampshire and South Carolina and shifted the money to Iowa.

A super PAC run by his allies, called Unite the Country , has scrambled to boost Biden's prospects in the Hawkeye State, running about $4.8 million in ads, according to Kantar Media's Campaign Media Analysis Group.

New campaign finance reports show the group raised nearly $3.8 million in 2019, with about one-quarter of its haul, $1 million, coming from a single individual: George Marcus, a real estate billionaire from Palo Alto, California. Other donors included Roger Altman, a former Clinton administration official and founder of investment bank Evercore; and Dick Harpootlian, a South Carolina lawyer and Biden loyalist.

On Friday, the group announced that new January fundraising had brought the total raised to date to $7.6 million.