Two-thirds of the Democratic presidential candidates spent more than they raised in the last three months and have dwindling cash reserves — a serious warning sign for their viability heading into the expensive chase for votes in Iowa and other early states.

Among the candidates in the red last quarter was Joe Biden, who ended September with less than half the cash on hand, $9 million, of any of his top rivals. And while most other candidates have even less in their bank accounts, which could force some of them from the race before Iowa, the former vice president is set to be seriously outspent in the advertising and organizing battles that will soon ramp up in the first caucus state.

While Biden still polls at or near the top of the Democratic field, his finances lag significantly behind Bernie Sanders, Elizabeth Warren and Pete Buttigieg, who are sitting on nearly $83 million collectively and each spent the summer building up cash. Kamala Harris also has narrowly more campaign cash in the bank than Biden, though she is also carrying nearly $1 million in debt from deferred payments to consultants and lawyers.

The financial edge enjoyed by Sanders, Warren and Buttigieg is already translating into tactical advantages: Warren paid salaries to over 600 staffers over the summer, while Sanders approached that number, dwarfing the rest of the field. Buttigieg dropped $4.7 million on just digital ads last quarter, while also airing TV ads in Iowa and New Hampshire.