Former President Trump's latest fundraising figures, chock-full of massive grassroots contributions, prove that he remains the most prolific rainmaker in the Republican Party.

Trump’s various fundraising committees hauled in $51 million during the second half of last year, and the former president could boast a war chest with $122 million cash on hand as of the end of December.  

But Trump’s fundraising prowess is not magically transferring to many of the candidates he’s endorsed in the 2022 election cycle.

TRUMP HAULS IN $51 MILLION DURING SECOND HALF OF 2021

Former Sen. David Perdue announced on Monday night that he brought in $1.146 million in first 56 days of his gubernatorial campaign as he primary challenges conservative Gov. Brian Kemp. Perdue was dramatically outraised by Kemp, who, as Fox News first reported last month, raked in over $7 million during the second half of 2021. A Kemp spokesperson called Perdue's fundraising "embarrassing."

David Perdue

Former U.S. senator and Republican gubernatorial candidate David Perdue greets supporters at a campaign event on Feb. 1, 2022, in Dalton, Georgia.  (Elijah Nouvelage/Getty Images)

And Perdue’s fundraising total pales in comparison to Democratic candidate Stacey Abrams, who hauled in $9.2 million during the first two months of her second straight bid for Georgia governor.

"The folks who get Trump’s endorsement, everyone thinks that it just automatically gets you all of this cash. But you need to have an operation in place to order to collect it," a veteran GOP operative told Fox News.

"It was kind of stunning to see Perdue, who had a huge operation and raised millions upon millions in the Georgia Senate runoff elections a year ago, just couldn’t capitalize," noted the operative, who asked to remain anonymous to speak more freely.

GEORGIA GUBERNATORIAL BATTLE: STACEY ABRAMS HAULS IN OVER $9M

Perdue’s far from the only Trump-endorsed candidate who’s yet to light it up when it comes to fundraising.

In Arizona, Trump-endorsed gubernatorial candidate Kari Lake touted her "historic grassroots" fundraising. But Lake’s 2021 haul of $1.5 million trailed four other GOP candidates also vying for their party’s nomination.

And in Maryland’s GOP gubernatorial primary, Trump-backed state Del. Dan Cox was far outraised by GOP rival Kelly Schulz, a former state commerce secretary.

In the battle for the Senate, Rep. Mo Brooks of Alabama, who’s running for the GOP- held open seat in his home state, raised a paltry $382,000 during the final three months of last year. That’s far behind the total raised by one of his top rivals, Katie Britt, who hauled in $1.2 million during the same period. And Britt’s outraised Brooks $5 million to $2.2 million last year.

Trump and Mo Brooks

Former President Trump welcomes candidate for Senate and Rep. Mo Brooks to the stage during a rally at York Family Farms on Aug. 21, 2021, in Cullman, Alabama. (Chip Somodevilla/Getty Images)

In North Carolina, another race where the former president took sides in a contested GOP primary for an open Senate seat, Trump’s endorsement last June of Rep. Ted Budd didn’t initially fuel the candidate’s fundraising. It took until the October-December fourth quarter of fundraising for Budd to outraise his chief GOP rival, former Gov. Pat McCrory.

Republican Sen. Lisa Murkowski of Alaska, one of seven GOP senators who voted to convict the former president in his 2021 impeachment trial, more than doubled the fundraising last quarter of Trump-backed GOP challenger Kelly Tshibaka.

And in Nevada, former state Attorney General Adam Laxalt brought in $1.35 million in fundraising the past three months for his GOP bid to try and unseat Democratic Sen. Catherine Cortez Masto. Even though Laxalt raised more money than nearly any other Republican non-incumbent, his fourth quarter haul was only slightly ahead of the roughly $1 million raked in by Sam Brown, his chief rival for his party's nomination.

Fundraising, along with polling, is a much-watched indicator of a candidate’s popularity and strength.

"Finance reports and fundraising numbers are one of the most useful metrics to gauge to success, or lack thereof, of some of these campaigns, especially in some of these crowded primaries," longtime Republican strategist Colin Reed told Fox News.

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"President Trump revolutionized the Republicans ability to engage and activate small- dollar donors," Reed noted.

But the veteran of Republican presidential and statewide campaigns emphasized that "to date there’s been no evidence that that ability transcends to other candidates that he’s supporting."

Not all Trump-backed candidates are struggling with fundraising.

Arkansas gubernatorial candidate Sarah Huckabee Sanders, who was Trump’s longest- serving White House press secretary, had hauled in over $11 million as of the end of September.

Herschel Walker and Donald Trump

Former college football star and current senatorial candidate Herschel Walker speaks at a rally as former President Trump applauds in Perry, Georgia, Sept. 25, 2021.  (REUTERS/Dustin Chambers)

And last month Fox News was first to report that Herschel Walker had raked in nearly $10 million from his late-August launch through the end of December in his Senate bid in Georgia. 

FIRST ON FOX: HERSCHEL WALKER HAULS IN NEARLY $10 MILLION FOR SENATE BID

But the two candidates are more the exception than the rule.

The GOP operative who requested anonymity stressed that "it’s important to get Trump’s endorsement, but you have to be able to turn it into money, and some of these folks are really struggling."