Democratic presidential primary candidate Sen. Cory Booker brought in $6.6 million in campaign cash in the October-to-December quarter of fundraising in 2019 -- a record number for the New Jersey senator but far behind what the top-tier contenders for the Democratic nomination raised.

The modest haul by the senator is a slight increase over the $6 million he raised during the third quarter from July to September in 2019. It’s his best quarterly fundraising report to date.

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Meanwhile, Sen. Bernie Sanders of Vermont brought in a massive $34.5 million the past three months -- the best quarterly haul of any Democratic White House hopeful to date this cycle.

Former South Bend, Ind., Mayor Pete Buttigieg raised $24.7 million, and former Vice President Joe Biden brought in $22.7 million, which was also his best fundraising showing to date.

Sen. Elizabeth Warren of Massachusetts raised $21.2 million during the fourth quarter of fundraising -- a haul that was down roughly $3.5 million from the previous three-month period.

Booker’s figure also lags behind middle tier-contenders Sen. Amy Klobuchar of Minnesota -- who brought in $11.4 million -- and tech entrepreneur Andrew Yang, who hauled in $16.5 million. Those numbers were records for both candidates, respectively.

Booker, arguably one of the most gifted orators in the still-large field of Democratic White House hopefuls, has struggled to resonate in polling and last month failed for the first time to qualify for a presidential primary debate.

The senator’s campaign touted that more than half of the fourth quarter total came from first-time donors, and that 96 percent of those who contributed for the first time donated online. The campaign said that the average online donation was $22.98.

“We’re thrilled to have closed out 2019 with our best fundraising quarter yet, despite not being able to join the December debate stage due to the artificial thresholds that prevented viable candidates from participating,” campaign manager Addisu Demissie said.

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But taking aim at Booker’s rivals, Demissie said that, “to put it bluntly, we’re still behind the fundraising of a field of predominantly white candidates who have been able to haul in significantly greater sums of money or tap into their personal fortunes to fund their campaigns."

"In the wake of Julian Castro’s departure, we find ourselves at a juncture where what started out as the most diverse field of candidates running for president in our nation’s history is increasingly becoming one that does not reflect the rich diversity of our party and of our country," Demissie added.

Asked Thursday during a campaign stop in New Hampshire about how he could compete with candidates with much larger campaign cash advantages, Booker told Fox News that “money does not buy elections in New Hampshire or in Iowa. These are smaller states where people want to get to know you, feel your spirit.”

“Our surge is coming,” the senator predicted.

And with one month to go until the Iowa caucuses, Booker emphasized that he’s “peaking at the right moment.”

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Campaign cash, along with public opinion polling, is a crucial barometer of a candidate’s popularity and a campaign’s strength. Fundraising dollars can be used to run TV, radio and digital ads, beef up grassroots voter outreach and build up staff. And the fourth quarter fundraising figures -- the last quarterly report before Iowa kicks off the primary and caucus presidential nominating calendar on Feb. 3 -- will be heavily scrutinized by political pundits.