The presidential campaign of Sen. Bernie Sanders (I-Vt.) announced Thursday that it had raised $25 million in the month of January, making the final month before the Iowa caucuses its most lucrative fundraising month to date in this election cycle.

The enormous cash haul consisted of more than 1.3 million donations from 648,000 individual donors, 219,000 of whom were new, according to the campaign.

Sanders’s operation is immediately plowing the new funds into television and digital ads worth $5.5 million in early primary and caucus states, as well as new campaign staff hires. The ad investments will build on existing efforts in California and Texas, and buy ad spots in eight Super Tuesday (March 3) states where the campaign had not yet begun advertising: Arkansas, Colorado, Massachusetts, Minnesota, North Carolina, South Carolina, Tennessee and Utah.

The campaign touted its strong support from Americans of relatively modest means, noting that teachers were the most common occupation of donors once again in January. The five most common employers of Sanders’s January donors were Amazon, Starbucks, Walmart, the U.S. Postal Service and Target, according to the campaign. The average donation was $18.72.

“Working class Americans giving $18 at a time are putting our campaign in a strong position to compete in states all over the map,” campaign manager Faiz Shakir said in a statement.

Joe Raedle/Getty Images Sen. Bernie Sanders (I-Vt.) speaks to voters in Derry, New Hampshire, on Wednesday. He remains the polling favorite days before the state's primary on Tuesday.

To date, Sanders has been the most prodigious fundraiser in the Democratic presidential field with a total haul of more than $121 million, including January, according to the campaign. In the final quarter of 2019, Sanders raised $34.5 million.

What two of Sanders’s rivals lack in direct fundraising, however, is offset by the support of super PACs capable of raising and spending unlimited sums to support them, so long as the outside groups do not coordinate with the candidates’ campaigns. Unite the Country, a super PAC supporting former Vice President Joe Biden, spent at least $3.8 million on his behalf. The liberal veterans group VoteVets PAC has spent hundreds of thousands of dollars on ads that favor former South Bend, Indiana, Mayor Pete Buttigieg ― an effort that a campaign aide apparently found a way to encourage on Wednesday within the notoriously porous letter of campaign finance law.

Sanders said he has rejected outside help. He has nonetheless received nearly $280,000 in support from the super PAC operated by the National Nurses United labor union. The union, which endorsed Sanders in November, spent the funds on radio ads and text messaging to boost his campaign.

At least one outside group has used big-dollar donations to finance attacks against Sanders. A pro-Israel super PAC affiliated with Democratic Majority for Israel spent nearly $700,000 on a last-minute TV ad campaign in Iowa that questioned Sanders’s ability to defeat President Donald Trump in November. Sanders responded to the effort with fundraising appeals to supporters that netted more than $1.3 million in 24 hours.

Buttigieg’s campaign has criticized Sanders’s self-styled image as a foe of corrupt campaign finance practices, calling him out in fundraising emails for receiving the support of “dark money” groups. But a political nonprofit affiliated with the left-wing group Justice Democrats, which does not have to disclose donors, has not endorsed Sanders. It is spending $500,000 on a digital ad campaign slamming his rivals Buttigieg and Biden.

A coalition of nine pro-Sanders progressive groups announced plans last week to mount an independent spending effort on Sanders’s behalf. But the coalition, called People Power for Bernie, which would use a vehicle that does not require it to disclose donors, has yet to provide a dollar figure estimate for its investment or clarify whether it will disclose donor identities voluntarily. (The NNU’s super PAC has to disclose its donors and is thus not considered a “dark money” group.)

Sanders heads into the New Hampshire primary on Tuesday with a significant lead in the average of public polls.

His campaign’s announcement of the January haul is nonetheless an effort to generate more momentum after Monday’s Iowa caucuses.

As of late Wednesday, with 97% of Iowa precincts reporting, Buttigieg held a razor-thin lead over Sanders in the state convention delegate count that the Iowa Democratic Party has historically used to determine a caucus winner.

But the complexity of Iowa’s delegate allotment system means that a candidate can win the final popular vote, which Sanders was leading in as of Wednesday night, without prevailing in the state’s version of an electoral college.

As a result, the raw data from those precincts showed Sanders winning both the first and second rounds of the statewide popular vote ― or final realignment forged after supporters of candidates who did not meet a “viability” threshold of votes went to other candidates’ camps.

Though the Iowa Democratic Party’s results reporting fiasco denied either Buttigieg or Sanders the opportunity to claim an unalloyed win on Monday night, both camps have sought to shape the narrative in their favor, with Buttigieg initially declaring himself “victorious” and the Sanders campaign releasing internal data showing the Vermont senator leading in all aspects of the caucus.

In a letter to Sanders staff, volunteers and surrogates in Iowa, Misty Rebik, Sanders’s Iowa state director, highlighted the campaign’s success in some of the most youthful and racially diverse precincts in cities like Des Moines, as well as its success in rural areas like Buena Vista County. The campaign won 11 out of the 12 precincts released thus far where Latinos make up over 20% of registered voters, according to the Sanders campaign’s analysis of official data.