In California’s crowded race for governor, Xavier Becerra has quickly risen in the polls, capitalizing on a message centered on his extensive experience in government, including stints as U.S. health and human services secretary, the state’s attorney general and a member of Congress.

“I’ll make sure as governor I tackle these crises because I’ve been through these crises before and had to handle them,” Becerra said at a gubernatorial debate last month. “We need someone with experience, someone who doesn’t need on-the-job training.”

But that argument has drawn an onslaught of criticism from Becerra’s fellow alumni of the Biden administration, including some who worked closely with him, over his leadership of HHS and how he handled multiple crises during his tenure.

The line of attack presents a major test for Becerra, who’s risen to the top of the polls in the final stretch of California’s turbulent gubernatorial contest, as he seeks to prove to voters he is best suited for the task of managing the most populated state in the country.

“In moments of real challenge, that’s kind of when you mark: Are you able to step up? He did not have the grasp of the agency or the role that I think you want in an executive,” said a former White House official under then-President Joe Biden who worked closely with matters involving the Department of Health and Human Services.

“HHS is one of the most challenging bureaucracies because it’s so huge, and it has all of these independent agencies as part of it that you have to make sure that an executive-style person is in charge and who is able to manage that,” continued the former official, who was granted anonymity to speak candidly. “And he did not have the capabilities to do that.”

Becerra faced a number of challenges as health and human services secretary, most notably managing the Covid pandemic. HHS was also the lead agency in charge of dealing with the surge of unaccompanied migrant children at the U.S.-Mexico border, a pandemic-created shortage of baby formula and a 2022 outbreak of the mpox virus.

On the issue of Covid, the former administration official said Becerra should have done more to help coordinate a clearer messaging strategy in disseminating what was often conflicting public health guidance on issues like social distancing.

“There was debate and disagreement among all of those government scientists and public health officials about the best way to kind of get that forward, and he really wasn’t able to shepherd that,” the person said. “He just wasn’t up for it.”

The official added that Becerra, as well as others throughout the administration, were “asleep at the wheel” when it came to the baby formula shortage.

Another former Biden administration official said that Becerra didn’t adequately tackle efforts to handle the migrants who were arriving in droves at the border.

“You just saw this huge backflow of unaccompanied children overflowing” in Customs and Border Protection facilities, “because HHS was not really able to do what it needed to do to hold up its end of the formula,” that person said.

That person said that Becerra’s stewardship of HHS — a sprawling agency that at the time had about 80,000 employees — is particularly relevant to his gubernatorial campaign, given that he would oversee an even broader government bureaucracy if elected. California currently has around 250,000 state civil service employees.

“California is a huge state with very complex bureaucracies, very complex, sweeping agencies that all fall within the governor’s purview,” the person said. “His experience leading such complex entities, his track record on that is not great.”

“I’m not sure his experience there has, you know, set the stage for him to be governor of one of the world’s largest economies — I just think that’s not his skill set,” the person added.

Last week, Xochitl Hinojosa, who led the Justice Department’s public affairs office for two years during the Biden administration, also sharply criticized Becerra on CNN.

“He was not effective in government, and I think that a lot of people in the Biden administration are talking about this because they realize that he was not an effective HHS secretary,” she said. “And if you ask any Cabinet secretary, they will tell you the same thing.”

Becerra campaign spokesperson Jonathan Underland and campaign adviser Michael Bustamante hit back against the attacks from both the unnamed and named Biden administration members, while providing NBC News with a raft of other former colleagues who praised Becerra.

In one such statement, former Energy Secretary Jennifer Granholm said that, “When it came to the greatest challenges of our time — a global pandemic, expanding coverage, lowering costs — he led with courage and expertise.”

In another, former Labor Secretary Julie Su praised Becerra as a “tireless champion for working people and families, and I’ve seen that firsthand.”

And Neera Tanden, a senior adviser to Biden in the White House, hit back directly against Hinojosa’s criticism, writing on X, “I worked directly with Becerra, often daily, and this is bs.”

“He delivered on Medicare Drug negotiation, $35 insulin and got health care coverage for 14 million more people. We appreciated that he got big things done,” she added.

Granholm and Su have formally endorsed Becerra, while Tanden has offered support for him but has not issued an official endorsement in the race.

Some of the criticisms of Becerra were made at the time he held the top job at HHS. NBC News also reported in December 2021 that Becerra kept a low public profile in fighting the pandemic.

More recently, some of Becerra’s former colleagues in the Biden White House have declined to back his campaign. Former Homeland Security Secretary Alejandro Mayorkas said in an interview with Politico that he was “agnostic with respect to the California gubernatorial race right now.” That came just days after former Vice President Kamala Harris issued a slate of endorsements in races up and down the ballot in her home state of California — but not in the race for governor.

The criticisms of Becerra have intensified as he’s rapidly risen in the California governor’s race following former Rep. Eric Swalwell’s abrupt exit last month. With just weeks to go before the June 2 all-party primary and with mail-in ballots already sent out, Becerra now sits near the top of all recent polling, along with fellow Democrat Tom Steyer and Republicans Steve Hilton and Chad Bianco, though the contest still lacks a clear front-runner. The top two voter-getters will advance to a general election, regardless of party.

During the final debate before the primary Thursday, San Jose Mayor Matt Mahan, another Democratic candidate in the race, lambasted Becerra for not handling the pandemic well.

“He wasn’t minding the shop, the Biden administration had to sideline him from Covid — this is not the leadership you need,” he said.

“This is what happens when you take the lead in the polls,” Becerra replied at another point, amid a slew of additional attacks. “They all come at you.”

Becerra’s campaign has also dealt with several other controversies since vaulting to the top of the pack.

A California political consultant to Becerra, who also served as Gov. Gavin Newsom’s chief of staff, pleaded guilty Thursday to a plot to steal campaign funds from a dormant Becerra campaign account. Becerra’s chief of staff at HHS had also pleaded guilty in December to stealing campaign funds from that Becerra account.

Becerra has said he didn’t know about the thefts and in a statement Thursday, he reiterated that he wasn’t involved.

“As I said from day one, I was not involved, I did nothing wrong. And now the record confirms it. We can close the book on this,” he said.

The scandal has been the subject of attack ads run by the Steyer campaign in recent weeks, and at Thursday night’s debate, Becerra drew fire from several of his opponents on the issue.

Democratic former Rep. Katie Porter suggested that Becerra could still face charges, saying the latest plea “does not preclude an indictment from being issued against you.”

And this week, Becerra faced blowback for how he handled an interview with Los Angeles TV station KTLA.

In a clip that was circulated on social media, Becerra asked the reporter, “By the way, this is a profile piece, this is not a ‘gotcha’ piece, right?”

“The way I describe profile is: You talk about all the things I’ve done, things I want to do, along with some tough questions. But not only tough questions,” he said.

Steyer brought up the interview during a recent campaign event and posted the clip on X.

“You ask me a tough question — if it hurts, I will answer it. And that’s the thing Xavier Becerra has not been willing to do,” he said. “You can’t duck the hard questions.”

Underland, the Becerra campaign spokesperson, told NBC News that “the measure of a good governor is whether they can take the hits, get back up and keep on swinging.”