Joe Biden lagged behind other 2020 Democratic rivals in campaign spending in the months before the mad dash to the Iowa caucuses and entered the year with a small war chest.

Federal Election Commission filings for the Democratic presidential candidates released Friday show that the former vice president entered the month of January with about $9 million in cash-on-hand, while Massachusetts Sen. Elizabeth Warren had $13.7 million, former South Bend, Indiana, Mayor Pete Buttigieg had $14.5 million, and Vermont Sen. Bernie Sanders, 78, had the largest war chest at $18.2 million.

The limited funds could mean trouble for Biden as he scrambles to show a strong finish in the Feb. 3 Iowa caucuses as Sanders rises in Iowa polls. The RealClearPolitics average shows Sanders leading among likely caucusgoers in the state at 23.8%, while Biden is in second place at 20.2%, Buttigieg has 15.8%, and Warren is at 14.6%.

With limited funds, Biden, 77, could struggle to deploy advertising, volunteer, and get-out-the-vote efforts in the state compared to his rivals. Biden is closely matched with his competitors in the number of staff members and field offices in Iowa, but other signs indicate that there is dampened enthusiasm for his campaign, and Sanders's campaign could be surpassing him in volunteer efforts.

The FEC filings reveal, however, that Biden's rivals are scrambling to perform well in the first nominating contest states, each spending more from October through December than they raised.

Warren, 70, spent $12.1 million more than the $21.3 million she raised in that time, Buttigieg spent $8.9 million more than the $24.7 million he raised, and Sanders spent $15.3 million over the $34.4 million he brought in during the quarter. Biden, on the other hand, spent slightly less during the quarter as the $23.3 million he raised, suggesting that he expects longevity in the race.

The high burn rates demonstrate the importance of a good showing in Iowa, which is thought of as a way to prove viability as a candidate. Since 1972, no candidate that placed lower than third in Iowa has gone on to with the Democratic presidential nomination.

Stakes are particularly high for Warren and Buttigieg, 38, each of whom topped Iowa polls at one point in the past three months but then steadily declined.