DES MOINES, IOWA -- DES MOINES, Iowa -- Billionaire Michael Bloomberg spent roughly $180 million in the month after his late entry into the Democratic presidential primary, a staggering sum that's drastically more than all other leading contenders spent during much of the past year combined.

Since his entry into the race in late November, the former New York City mayor has drawn withering criticism from rivals who accuse him of using his massive fortune, estimated to be $60 billion, in an attempt to buy the party's nomination. The spending, detailed in a campaign finance report that all candidates must submit to the Federal Election Commission on Friday, has enabled Bloomberg to dominate TV advertising and become a credible contender, even though he hasn't appeared in a debate and is not competing in many early voting states.

On Sunday, he will go head-to-head with President Donald Trump in dueling ads that air during the Super Bowl. Meanwhile, the other leading candidates have drawn down their cash reserves in a final push before the first-in-the-nation Iowa caucuses on Monday.

Money may not be an obstacle for Bloomberg. But the cash-on-hand sums reported by former U.S. Vice-President Joe Biden, former South Bend, Indiana, Mayor Pete Buttigieg and Sens. Bernie Sanders, Elizabeth Warren and Amy Klobuchar will offer a key indication of the health of their campaigns.

A poor performance during the caucuses on Monday combined with an anemic bank account balance could be a death knell for a campaign, or at least make it difficult to persuade donors to give more money.

"For the guys and gals who have spent substantial resources getting to this stage in Iowa, if they don't meet expectations, they are going to be in a position where they have to live off the land in the coming weeks, which is not a fun place to be," said Danny Diaz, a Republican consultant who was a senior adviser for Mitt Romney's 2012 White House bid and the manager of Jeb Bush's 2016 presidential campaign.

The totals reported Friday will show where the candidates stood at the end of 2019 and don't reflect the month of spending in the sprint before the caucuses. Sanders spent $50 million over the last three months of the year and had the most cash still on hand, with $18.2 million. Buttigieg reported that he spent $34 million during that time and had $14.5 million cash on hand, while Warren spent $33 million with $13.7 million left. Klobuchar had $4.9 million in reserve after spending $10.1 million during that period.

Biden has not yet filed his report, which was due by midnight Friday.

Those who rely on traditional donors to fund their campaigns will likely face additional headwinds coming out of Iowa unless they bring in new donors because some of their most ardent supporters have already given the $2,800 maximum. The two leading progressives in the race, Warren and Sanders, on the other hand, have relied on an army of small-dollar grassroots donors chipping in small amounts -- a source of campaign cash that doesn't easily max out.

"If one underperforms (in Iowa) and you're strapped for cash, you're probably going to crash and burn," said David Brock, a major Democratic fundraiser who leads two outside groups that are targeting Trump in the general election. "It may be that we see even further winnowing of the field soon."

In October, Biden reported that he had just $9 million on hand at the end of September, which was far less than Warren, Sanders and Buttigieg. On Friday, his campaign announced in a memo to supporters that January was their strongest fundraising month since the launch of his campaign. But campaign manager Greg Schultz also downplayed the importance of being a leading fundraiser.

A super PAC founded by Biden allies reported that it spent $2.9 million of the $3.7 million it raised by the year's end. The group, which legally cannot co-ordinate with Biden's campaign, said in a news release that it has since taken in a total of $7.6 million, most of which was spent on ads in Iowa. Steve Schale, a strategist for the group, did not respond to a request for comment.

"Elections ultimately are not about money, they're about having the right message and vision for the country. But you have to have the resources to compete, which we unequivocally do," Schultz wrote in the memo.