SACRAMENTO, Calif. >> Four years ago, when a veteran California congressman, Xavier Becerra, came home to become the state’s attorney general, eyebrows rose — not in disapproval, but surprise.

News reports referred to then-Gov. Jerry Brown’s “unexpected” pick to finish out the unexpired term of the state’s new senator, Kamala Harris. Fellow politicians wondered why he would leave Washington, where he had been working for 24 years toward a top leadership position in Congress. But Becerra leapt into the fray as California’s lead attack dog in the Trump resistance, filing roughly 100 lawsuits against the administration on everything from climate change to the Affordable Care Act.

“I’m not sure he was the logical choice,” another former California governor, Gray Davis, said Monday. “But he did a hell of a job.”

With the announcement that President-elect Joe Biden has selected Becerra as his nominee for the secretary of health and human services, Becerra, one of the country’s best-known Latino politicians, is again surprising people. Some of the medical experts who had urged Biden’s team to name someone with public health expertise were “astounded” at Becerra’s nomination, one of them said.

But longtime supporters and old friends in California said Becerra was perfectly suited to a job that required not only an ability to lead a large organization but also an intimate knowledge of how badly many Americans, particularly essential workers, have suffered under the current administration’s policies on health insurance and the pandemic.

“He’ll be all-in because he is so committed,” Brown said. “Not just to the Affordable Care Act, but to health care and equity in general. And he knows his way around Washington.”

Certainly Becerra has been committed in recent years to fighting the White House on behalf of Californians, filing a barrage of lawsuits to protect immigrants, the environment, gun control and many other priorities that the state prizes as fundamental to its way of life. He has sued to stop the repeal of an Obama-era order that protected immigrant “Dreamers” who came to the United States as children and grew up without legal status. He has challenged the Trump administration’s attempt to roll back California’s authority to set its own rules on climate-warming tailpipe emissions.

Becerra has filed more than a dozen lawsuits about health alone, including one in which California led 20 states and the District of Columbia in a campaign against Republicans who sought to legally gut the Affordable Care Act — a law in which California, with a third of its population relying on the state’s version of Medicaid for health care, has an enormous stake.

Becerra also created a first-of-its kind state-level environmental justice bureau, focused on the unequal effect that pollution and other forms of environmental damage have on health in the most vulnerable communities.

And he settled a landmark antitrust case against Sutter Health, a Northern California network of doctors and hospitals, which agreed to pay out $575 million in damages and have its business operations monitored for 10 years. The lawsuit originally filed by a grocery workers’ union health plan claimed that Sutter’s anticompetitive behavior was driving up health costs.

The suit was a “paradigm case” on behalf of consumers, said Matt Cantor, a lawyer at Constantine Cannon, a New York firm that worked with Becerra’s office on a related suit. That Becerra chose to bring it, he said, “shows that he’s very concerned about what the average American family and average American employer has to pay in health insurance premiums.”

A native of Sacramento, Becerra is the son of immigrant parents; his mother emigrated from Mexico as a young woman and his father was born in Sacramento but raised in Tijuana. They married at 18 and moved to California, where the elder Becerra worked picking vegetables and laboring in construction — experience that friends say will shape how Becerra inhabits his job as health secretary.

“I think that it gives him a certain perspective and humility and an appreciation for working people, for ordinary people,” said Rep. Joaquin Castro of Texas, chairman of the Congressional Hispanic Caucus, who said Becerra mentored him and other Latino newcomers on Capitol Hill. “And when you talk to Xavier you see that he’s not a pretentious person.”

At McClatchy High School in Sacramento, he was a high achiever whose extracurriculars included golf, which he taught himself to play, and a leadership group that focused on conflict resolution. “He was a really well-rounded guy — an athlete and a nerd and a leader,” said Karen Skelton, a California political consultant who went to school with him.

He was the first in his family to attend college, graduating from Stanford University in 1980 and Stanford Law School in 1984. In interviews, he has said that he applied to the elite school only because he had filled out a blank application a friend had discarded, and that it was not until he drove with his mother to affluent Palo Alto that he realized his family was not middle class. There, he met his wife, Carolina Reyes, who is now an obstetrician specializing in high-risk pregnancies.

Their three daughters are grown; friends note that although Becerra’s father had little formal education, the attorney general’s children earned their undergraduate degrees from Yale and Stanford universities, and at least two have graduate degrees.

Although Becerra was not a name put forward by Biden’s medical advisers, a person familiar with the selection process said the president-elect was impressed with his management experience and his legal advocacy on behalf of the Affordable Care Act — President Barack Obama’s signature health care law, which Biden, then vice president, worked to get passed in 2010.

Biden was also said to be taken with Becerra’s personal story, which he views as much like his own; his commitment to social justice; and his record of working across party lines. The two men knew each other from their shared time on Capitol Hill, and Biden did not have to introduce himself when he offered the job to Becerra on Friday evening.

“He took note of how, like himself, Becerra came from a working-class family and also like himself Becerra was the first person in his family to graduate from college,” said the person who described the process. “And he was also taken with how, shortly after graduating from Stanford Law, Becerra started giving back and giving legal aid to clients who had mental health care needs.”

“Oh, he’s the Latino Joe Biden,” agreed Art Torres, a former state senator who hired Becerra to work in his Los Angeles district office in 1986, and who became an important mentor. “Working-class kid, the product of hard work. I used to kid him because he was the only guy I knew who still drank milk with his lunch. That’s how much of a Boy Scout he was.”

That said, Torres joked, “I don’t know what he drank with dinner.”

After a stint as a deputy attorney general, in the mid-1980s, Becerra was tapped by Torres and other Latino leaders in Los Angeles to run for an open state Assembly seat — part of a cadre of young Latino activists looking to replace the old-guard Latino establishment in Southern California.

He ran as a law-and-order candidate, and helped pass a bill into law that lengthened prison terms for gang members caught committing crimes on or near school property. But just weeks into Becerra’s freshman term, Rep. Ed Roybal, a Los Angeles Democrat, announced his retirement.

The ambitious Becerra announced his candidacy even though he did not live in Roybal’s district — drawing accusations that he was a carpetbagger — but went on to represent the downtown-area district for 24 years.

In Congress, Becerra landed a coveted slot on the powerful Ways and Means Committee, which is responsible for tax policy, becoming the first Latino to serve on the panel. He served on both the health and Social Security committees, and helped draft legislation on those issues.

Like many Democrats, he voted against the passage of a 2003 Republican-led bill expanding Medicare to include prescription drug coverage for older adults; he viewed the measure, which precluded the government from negotiating with drugmakers, as a giveaway to the pharmaceutical industry.

Less than a decade later, he joined Speaker Nancy Pelosi in pushing for passage of the Affordable Care Act.

He was said to be aiming for a top House leadership position when Brown tapped him after the 2016 election to succeed Harris as attorney general, overseeing an office of some 4,500 lawyers.

“I wanted someone with intellectual horsepower, but I also wanted a down-to-earth guy,” Brown said.

On Monday, with one foot out the door, Becerra was still condemning the Trump administration from his day job in Sacramento, filing an amicus brief in a case challenging the administration’s oversight of toxic chemicals and lashing out against federal pollution standards.

“It’s despicable,” Becerra said in a statement. “Across the country, our relatives and neighbors in low-income communities are bearing the brunt of particulate matter pollution and the resulting health consequences. Today, the Trump administration’s callous disregard for their lives is on full display.”

Meanwhile, conservative critics were condemning Becerra, with anti-abortion groups such as the Susan B. Anthony List calling on Twitter for Republican senators to “stand firm & stop this unacceptable nomination.”

Among early conservative complaints was Becerra’s stance on Medicare for All, the single-payer government-run health insurance plan promoted by Sen. Bernie Sanders, who challenged Biden for the Democratic nomination for president. Becerra has supported it. Biden does not.

But on Monday, supporters in Washington and California downplayed those differences.

“Attorney General Becerra is a towering champion of health care, whose strategic leadership, keen intellect and outstanding policy expertise were essential in the defense of the Affordable Care Act in the courts,” Pelosi said in a statement. “As secretary of the Department of Health and Human Services, he will be a vital force for progress.”

And in Sacramento, California’s governor, Gavin Newsom, lauded the choice as a breath of “the fresh air of progress.”

“It’s a game-changer for us,” he said. “We’ve had our eye on some big reforms. We’ve been looking for a great partner. And we’ve found one.”

Dr. Ada D. Stewart, a South Carolina family practice doctor and the president of the American Academy of Family Physicians, had been one of those hoping Biden would put a doctor in the health secretary’s job. But Becerra, she said, is the next best thing: “Someone who has the same priorities and the same principles” as her organization, she said. “Health care for all.”