WASHINGTON — Alejandro N. Mayorkas, President-elect Joseph R. Biden Jr.’s pick to lead the Department of Homeland Security, said at a Senate confirmation hearing on Tuesday that he would bolster efforts to combat domestic terrorism, and he parried Republican questions on his past handling of visas for wealthy foreign investors.
But hanging over the hearing was another issue that was at the center of the Trump administration’s agenda and could become the first big fight in the Biden era: what to do about the nation’s strained immigration laws and the remnants of President Trump’s restrictionist border controls.
After it ended, Senator Josh Hawley, Republican of Missouri, announced he would block any Democratic effort to swiftly move Mr. Mayorkas’s nomination to a confirmation vote.
“Mr. Mayorkas has not adequately explained how he will enforce federal law and secure the southern border given President-elect Biden’s promise to roll back major enforcement and security measures,” Mr. Hawley said in a statement.
The hearing for Mr. Mayorkas, who would be the first Latino and first immigrant secretary of homeland security, came as thousands of migrants set off from Honduras in recent days to travel to the United States, prompting questions over how Mr. Biden will approach border issues that dominated the Trump years.
Mr. Mayorkas’s nomination has also received renewed interest from Democrats and former national security officials, concerned by the significant failures in security preparedness that helped lead to the deadly assault on the Capitol this month.
“The love for this country that I learned from my parents made the Jan. 6 attack on the Capitol all the more horrifying,” Mr. Mayorkas said in his opening remarks. “I will do everything I can to ensure that the tragic loss of life, the assault on law enforcement, the desecration of the building that stands as one of the three pillars of our democracy, and the terror felt by you, your colleagues, staff and everyone present, will not happen again.”
Mr. Mayorkas, a deputy secretary of homeland security under President Barack Obama, has received support both from immigration advocates and law enforcement officials for the experience he would bring to a department that has been without Senate-confirmed leadership for nearly two years. The agency became an arm of the Mr. Trump’s restrictionist immigration agenda over four years that featured six leaders.
But it was Mr. Mayorkas’s previous work at the department that prompted criticism from Republicans on the Senate Homeland Security and Governmental Affairs Committee.
Senator Rob Portman, Republican of Ohio, opened the hearing by pressing Mr. Mayorkas on an inspector general report in 2015 that found he had helped expedite visa reviews for foreign investors while leading the department’s legal immigration agency, Citizenship and Immigration Services.
The inspector general, prompted by internal complaints from employees, found Mr. Mayorkas had become personally involved in three cases in a program that provides visas to certain foreigners who invest in American businesses. The businesses included a hotel and casino promoted by Harry Reid, the former Democratic majority leader, a Los Angeles film project involving former Gov. Ed Rendell of Pennsylvania, also a Democrat, and an electric car company led by a former Democratic governor in Virginia, Terry McAuliffe, and Tony Rodham, the brother of Hillary Clinton.
The report did not find that Mr. Mayorkas broke the law but that he did leave “an appearance of favoritism and special access.”
Mr. Mayorkas said on Tuesday that he felt obligated to involve himself in a system “plagued by problems.” He said there were “hundreds of cases that I became involved in at the request” of members of Congress.
“It is my job to become involved, learn the problems that the agency confronts, to become involved in those problems and to fix them,” Mr. Mayorkas told the committee. “That’s what I did in this case and the many cases that came before me and were presented to me on both sides of the aisle.”
Just weeks after Mr. Trump incited an angry mob that stormed the Capitol, the committee pressed Mr. Mayorkas on how the Homeland Security Department would combat threats of white supremacy and right-wing extremism. The leadership of the department under Mr. Trump was accused by the agency’s former intelligence chief of downplaying the threat of white supremacy and trying to amplify left-wing violence — charges the agency has denied.
“The Trump administration did not do a good job in addressing this very real threat and a threat we saw play out in Black churches, mosques and synagogues over the past few years,” Senator Gary Peters, Democrat of Michigan, told Mr. Mayorkas.
Mr. Mayorkas said he would support the department’s intelligence branch.
“The threat of domestic extremism is one of the greatest threats the Department of Homeland Security confronts, and it has unique capabilities in confronting it,” Mr. Mayorkas replied. “I look forward to playing a critical role in empowering the Office of Intelligence and Analysis in an apolitical, nonpartisan way.”
Senators also grilled Mr. Mayorkas on how he would balance maintaining control at the border with Mr. Biden’s pledge to unwind many of Mr. Trump’s policies that have effectively halted an asylum system meant to provide protection for those fleeing persecution.
When Senator James Lankford, Republican Oklahoma, asked him if he would support dismantling parts of Mr. Trump’s border wall, he was evasive.
“The border is varied depending on the geography, depending on the specific venue and depending on the conduct of individuals around it,” Mr. Mayorkas said. “We don’t need nor should we have a monolithic answer to that varied and diverse challenge.”
He instead reiterated Mr. Biden’s previous statement that he would not construct another mile of it. He also committed to ending a Trump administration program that forced migrants to remain in Mexico as their immigration cases make their way through the courts, although he did not specify a timeline.
Mr. Mayorkas also told Mr. Lankford that he had no intention of dismantling immigration enforcement agencies, including Immigration Customs Enforcement or Customs and Border Protection, a call that has been embraced by some Democrats on the party’s left flank.
“I would not abolish them,” Mr. Mayorkas said.
Mr. Mayorkas also dodged a question about whether he supported a public health emergency declaration the Trump administration has used to seal the border to asylum-seeking migrants and rapidly return them to Mexico or their home countries.
Senator Mitt Romney, Republican of Utah, pressed Mr. Mayorkas on whether he would grant entry to a caravan of migrants that is trying to travel north from hurricane- and pandemic-ravaged Honduras.
“If people qualify under the law to remain in the United States, we will apply the law,” Mr. Mayorkas said. “If they do not qualify, then they won’t.”