WASHINGTON  — President-elect Joe Biden has picked California Attorney General Xavier Becerra to be his health secretary, putting a defender of the Affordable Care Act in a leading role to oversee his administration's coronavirus response. 

If confirmed by the Senate, Becerra, 62, will be the first Latino to head the Department of Health and Human Services, a $1-trillion-plus agency with 80,000 employees and a portfolio that includes drugs and vaccines, leading-edge medical research and health insurance programs covering more than 130 million Americans.

As California's attorney general, Becerra has led the coalition of Democratic states defending "Obamacare" from the Trump administration's latest effort to overturn it, a legal case awaiting a Supreme Court decision next year. 

A former senior House Democrat, Becerra played a role in steering the Obama health law through Congress in 2009 and 2010. At the time he would tell reporters that one of the primary motivations for him was having tens of thousands of uninsured people in his Southern California district.

A number of prominent Democrats took to Twitter Sunday night to congratulate Becerra.

Jaime Harrison, the Democrat who challenged Sen. Lindsey Graham in South Carolina, said Becerra would make a "great selection" to lead the department.

California Gov. Gavin Newsom said Becerra has spent his "entire career fighting for equality and justice," and "spent the last four defending" the Affordable Care Act.

"Now, you‘ll help lead our nation toward quality, affordable healthcare for ALL -- and continue to make CA proud," he wrote.

Rep. Adam Schiff said "President-elect Biden could not have picked a better HHS Secretary than Xavier Becerra," noting his role in the fight to protect the Affordable Care Act.

Rep. Rashida Tlaib said it's "exciting" to have a Medicare For All advocate leading the department.

Overseeing the coronavirus response will be the most complicated task Becerra has ever contemplated. By next year, the U.S. will be engaged in a mass vaccination campaign, the groundwork for which has been laid under the Trump administration. Although the vaccines appear very promising, and no effort has been spared to plan for their distribution, it's impossible to tell yet how well things will go when it's time to get shots in the arms of millions of Americans.

The core components of HHS are the boots on the ground of the government's coronavirus response. The Food and Drug Administration oversees vaccines and treatments, while much of the underlying scientific and medical research comes from NIH. The Centers for Disease Control and Prevention takes the lead in detecting and containing the spread of diseases. The Centers for Medicare and Medicaid Services provides insurance coverage for more than 1 in 3 Americans, including vulnerable seniors, as well as many children and low-income people.

Under President Donald Trump, CDC was relegated to a lesser role after agency scientists issued a stark early warning that contradicted Trump's assurances the virus was under control, rattling financial markets. The FDA was the target of repeated attacks from a president who suspected its scientists were politically motivated and who also wanted them to rubber-stamp unproven treatments.

As California's attorney general, Becerra jokingly became known in Democratic legal circles as the man who sued Trump more than anyone else. Beyond health care, the lawsuits centered on issues from immigration to environmental policies.

Before he became California's attorney general, Becerra had served for more than a decade in Congress, representing parts of Los Angeles County. He had also served in the California state assembly after attending law school at Stanford.

His mother was born in Jalisco, Mexico, and emigrated to the U.S. after marrying his father.

The Associated Press contributed to this report.