ABC News' Mike Levine reports:
Under a cloud of Republican Party suspicion, President Obama's choice for deputy homeland security chief today denied that he improperly helped a politically connected foreign investor obtain a U.S. visa.
"I say it unequivocally, and I say it after 16 years of service to this country: I have never, ever in my career exercised undue influence to [change] the outcome of a case," an often-somber Alejandro Mayorkas told a Senate panel, his voice halting at times. "I have never based my decisions on who brings a case, but rather upon the facts of the law."
Mayorkas, who currently leads the U.S. Citizenship and Immigration Services agency, is one of several officials under internal investigation by the Department of Homeland Security's internal watchdog.
Specifically, the department's inspector general is looking into allegations raised last year that Mayorkas intervened on behalf of an electric car company co-founded by Democratic operative Terry McAuliffe, now a candidate for Virginia governor. Frustrated by the slow pace of processing visa requests for investors, McAuliffe appealed to senior USCIS officials for help.
The top Republican on the Senate Homeland Security and Governmental Affairs Committee, Tom Coburn, R-Okla., said the allegations, "if true, may directly apply" to Mayorkas' fitness to serve as DHS deputy secretary - the No. 2 at the department. Mayorkas would likely take over, in an acting capacity, for DHS Secretary Janet Napolitano when she leaves in September.
"Holding this hearing in light of an active investigation into serious, relevant allegations of professional misconduct by the nominee, and over the objections of the ranking member and others, appears to be virtually without precedent in the history of this or any other Senate committee," Coburn said in a statement.
Republicans boycotted today's hearing.
The committee's chairman, Tom Carper, D-Del., defended his decision to press on, saying the hearing allows lawmakers "to get answers in public and under oath."
Testifying under oath about his nomination, Mayorkas said allegations of impropriety are "unequivocally false," adding that he first learned about them Monday and still doesn't fully understand them.
Indeed, according to an email sent to lawmakers summarizing the investigation, the inspector general's office said it has yet to find any evidence of criminal conduct. Still, the office said it was also looking into allegations of "an appearance of impropriety by Mayorkas and other USCIS management officials."
Mayorkas hasn't been interviewed in the probe, but he is eager to weigh in, he said.
Carper and other Democrats launched a united defense of the president's nominee, describing the allegations as "a political brouhaha" based on "rumor, speculation and innuendo."
In addition, Carper said the inspector general's investigation might not be concluded for months.
At the center of the allegations against Mayorkas is a U.S. program that allows well-funded foreigners who are willing to invest in businesses in the United States to obtain a "green card" if their investments are likely to create U.S. jobs, Mayorkas described at the hearing.
First created by Congress in 1990, the EB-5 program has long been a target of criticism and controversy.
Mayorkas told lawmakers that the McAuliffe-related matter rose to his attention only because it involved a series of narrow, complex legal and policy questions. At one point, Mayorkas met with McAuliffe to hear his grievances, namely that applications for visas to foreign investors were taking so long to be processed.
USCIS officials originally rejected his company's application.
"I heard Mr. McAuliffe's complaints and I moved on with my work," Mayorkas said. "I do remember returning to [my] office and complaining about the fact that I had to hear complaints."
Mayorkas said it's "noteworthy" that such complaints continue to this day, so the people he allegedly improperly helped are still not satisfied.
At least one Democrat expressed optimism today that Mayorkas would be confirmed as DHS deputy secretary. Prior to leading USCIS, Mayorkas was a federal prosecutor for 12 years, notably becoming the U.S. attorney for the Central District of California. He also was a private lawyer in Los Angeles.
A top Republican has raised national security concerns over the EB-5 program.
"We need to be sure that the EB-5 program is not only creating economic stimulus and jobs, but that the nation's security isn't at risk," Sen. Charles Grassley of Iowa said in a statement Wednesday.
In one case cited by Grassley, a company tied to McAuliffe and Hillary Clinton's brother, Anthony Rodham, sought a visa for a vice president of Huawei Technologies Co., a Chinese telecommunications firm, investigated last year by the House Intelligence Committee for alleged ties Chinese intelligence services. The firm has previously denied those charges.
Company officials did not return a phone call or e-mail from ABC News seeking comment.
ABC News' Shushannah Walshe contributed to this report.