WASHINGTON — In between leading his law office’s response to the coronavirus and working on high-profile legal cases, Alejandro N. Mayorkas has spent the past four years studying the Trump administration’s immigration agenda, often answering questions from his law partners on the legality of President Trump’s policies.
His attentiveness should be helpful as he sets out to roll most of them back.
On Monday, President-elect Joseph R. Biden Jr. nominated Mr. Mayorkas to be the first Latino and first immigrant to lead the Homeland Security Department, the sprawling and troubled agency responsible for most of the nation’s policies on immigration, legal and illegal.
“It is no small task to lead the Department of Homeland Security, but I will work to restore faith in our institutions, and protect our security here at home,” Mr. Mayorkas said in a tweet.
Cuban-born and a veteran of the department, Mr. Mayorkas, if confirmed, would take the lead not just on enforcing immigration and border laws, but also on providing a coordinated response to terrorism, maritime, aviation and cybersecurity threats. A former director of the department’s legal immigration agency and a former deputy secretary of homeland security, Mr. Mayorkas was seen as the candidate who could best stabilize the department, which has spent much of the last four years in turmoil.
The department, which has been contended with vacancies and interim leaders, has been accused of bending to Mr. Trump’s political whims, whether that meant separating children from their families at the border, building a wall with Defense Department money or pulling protesters from the streets of Portland, Ore.
“A requirement for the department will be to heal after the last four years,” said Noah Kroloff, a former chief of staff for the Homeland Security Department who worked with Mr. Mayorkas during President Barack Obama’s first term. “Mayorkas, because he has experience at the highest levels of D.H.S., is very well positioned to do that.”
Former Obama administration officials advising Mr. Biden’s transition team have for weeks pushed for Mr. Mayorkas, 60, in part because of his immigrant story. He was born in Havana, and his family fled the Castro revolution.
Mr. Mayorkas was also one of the architects of a program that provides protections from deportation to 700,000 young immigrants brought to the country illegally as children, a policy the Trump administration has sought to dismantle.
Advisers said the nomination would satisfy moderate Democrats, Republicans and the many officers in the department, which oversees the agencies that carry out deportations and patrol the border, while not alienating liberal Democrats.
An official involved in staffing discussions said Lisa Monaco, Mr. Obama’s former homeland security adviser, is under consideration to become Mr. Mayorkas’s deputy.
Mr. Mayorkas has faced barriers in a path to confirmation before. After he was nominated to serve as deputy homeland security secretary, the department’s inspector general investigated him for intervening to help expedite visa reviews for foreign investors while leading U.S. Citizenship and Immigration Services.
Mr. Mayorkas was not found to have broken the law, but the inspector general released a report in 2015 that found that he managed cases for EB-5 visas in a way that led employees to believe he was giving special consideration to investors aligned with Democrats.
The report found that Mr. Mayorkas had intervened on behalf of investors with ties to Terry McAuliffe, a top Democratic fund-raiser and former governor of Virginia; former Senator Harry Reid, Democrat of Nevada; Edward G. Rendell, the former Democratic governor of Pennsylvania; and Anthony D. Rodham, the brother of Hillary Clinton.
Mr. Mayorkas conceded to Congress at the time that his intervention created an impression of political favoritism, but he said he was getting involved only to ensure the cases were decided correctly.
Chad Sweet, a former chief of staff for homeland security in the George W. Bush administration, said the incident was not likely to disenchant all of his fellow Republicans. Mr. Sweet said Mr. Mayorkas’s experience with cybersecurity while he was deputy secretary would appeal to many in law enforcement.
When Mr. Mayorkas led Citizenship and Immigration Services, he focused in part on rooting out fraudulent immigration applications, Mr. Sweet said.
“Do I think he’s more left of center than I would like? Yes,” Mr. Sweet said, adding, “There’s no question he’s qualified for the job, period.”
Rand Beers, a former acting secretary of homeland security in the Obama administration, said Mr. Biden’s pick made it clear that while immigration would be an early focus for the department, the new administration would also bolster its other responsibilities, such as cybersecurity and natural disasters.
Mr. Beers said Mr. Mayorkas balanced a vigilance of security threats with an interest in helping immigrants in need, pointing to his work vetting visa applications for Iraqis who assisted the U.S. military. Mr. Beers said Mr. Mayorkas pushed his teams to undergo exhaustive reviews of intelligence reports to scout for communications between applicants and suspected terrorists.
“He basically took that seriously and said we can’t ignore these reports but we also can’t assume the level of contact,” Mr. Beers said. “He’s thoughtful, he’s analytical and he’s humane.”
At the Homeland Security Department, Mr. Mayorkas led the agency’s response to the Ebola and Zika outbreaks, experience extremely relevant to this moment, the Biden transition team said on Monday. As homeland security secretary, Mr. Mayorkas would oversee the Federal Emergency Management Agency, which has played a prime role in helping state governments combat the coronavirus pandemic.
“He has seen all effects of Covid-19 in all segments of the economy and affecting all kinds of people, and he has been immersed in this for months,” said Jamie Gorelick, a partner at his law firm, WilmerHale, and former deputy attorney general in the Clinton administration. Ms. Gorelick tapped Mr. Mayorkas to lead the law firm’s coronavirus task force for clients.
Mr. Mayorkas has also been paying close attention to Mr. Trump’s efforts to overhaul the immigration system, Ms. Gorelick said.
He has spoken publicly about some of Mr. Trump’s moves, including the administration’s early attempts to wind down protections for young undocumented immigrants, known as Dreamers.
“They came here as children,” Mr. Mayorkas told “PBS NewsHour” in 2017. “They are graduates of high school, of colleges, of universities. They provide relief as first responders in Hurricane Harvey. They served our military. They’re part of the tapestry of American life.”
Pro-immigrant groups showed their support for the pick on Monday.
Janet Murguía, the president of UnidosUS, a Latino advocacy organization, said that “after four long, dark years” of the Trump administration and “a general contempt for Latinos from the highest office in the land, Mayorkas’s nomination signals a new day for the Department of Homeland Security and for all our country.”
Mr. Mayorkas graduated from the University of California at Berkeley and Loyola Law School. He is a fitness addict, spending free time running and playing tennis. He recently took up squash.
Even after Mr. Mayorkas left the department, he continued to communicate with its employees, Ms. Gorelick said. During business trips, she repeatedly spotted him making conversation with the Transportation Security Administration officers screening travelers at airports.
Katie Benner and Eric Schmitt contributed reporting.