If President Barack Obama names Thomas E. Perez as his next secretary of Labor, Senate Republicans will have a lengthy and contentious Washington track record to examine as they decide whether, or how strongly, to object to his nomination.

Perez, the assistant attorney general who heads the Justice Department’s Civil Rights Division, has served in that role since October 2009, when the Senate confirmed him on a bipartisan vote, 72-22. Since then, however, Perez has led the Obama administration’s notably aggressive prosecution of civil rights laws, frequently taking legal positions that have put him at odds with Republicans both in the states and in the halls of Congress.

His three-and-a-half-year tenure at the Justice Department is likely to be the subject of much scrutiny if he is nominated to lead the Labor Department — a job that itself could prove contentious as ongoing debates over the National Labor Relations Board, the federal minimum wage, immigration and other workplace-related issues begin to heat up.

“Secretaries of Labor haven’t been flash points for confirmation hearings at all,” said Cathy Ruckelshaus, legal co-director at the National Employment Law Project in New York, which is supportive of Perez as a potential nominee. But she warned that “it’s hard to tell what would happen in this context,” particularly given that Obama’s recent nominees to lead the Pentagon and CIA faced protracted battles before being confirmed.

The White House has declined to comment on the weekend’s widespread media reports that Obama will soon nominate Perez.

The Harvard-educated Perez, whose family emigrated to the United States from the Dominican Republic, would be the only Latino in Obama’s second-term Cabinet if he is named to succeed Hilda L. Solis, who resigned in January. He previously worked as Maryland’s Labor secretary, in the Office of Civil Rights at the Health and Human Services Department and as a special counsel to the late Sen. Edward M. Kennedy, D-Mass.

But it is his time at the Justice Department and, in particular, his experience in the middle of several controversial voting issues, that is likely to draw the most attention. Perez was the first Democrat since the passage of the 1965 Voting Rights Act to oversee the once-a-decade redistricting process and approve state-drawn maps.

He also led the department’s legal challenges against Republican-backed voting laws in Florida, South Carolina, Texas and elsewhere in 2012, often bluntly criticizing measures he said were intended to disenfranchise minorities, the poor and other voters. Republicans defended those measures as sensible efforts to protect the integrity of state elections from fraud.

In an interview with CQ Roll Call in 2011, Perez lauded the Civil Rights Division for its “heroic efforts to educate people about the do’s and don’ts of redistricting,” and voting rights advocates have praised his tenure at the Justice Department as a break from previous administrations.

“Tom’s Civil Rights Division was very, very responsive to the civil rights community,” said Nicole Austin-Hillery, director and counsel at the Washington office of the Brennan Center for Justice, which has worked with the department to challenge state voting laws.

If Perez is in for a bitter confirmation battle as a potential Labor secretary, he has shown that he will not back down from such public confrontations.

Last year, his division filed racial profiling charges against Joe Arpaio, the controversial Republican sheriff of Maricopa County, Ariz., and a polarizing figure in the national debate over immigration.

“At its core, this is an abuse of power case involving Sheriff Arpaio and a sheriff’s office that disregarded the Constitution, ignored sound police practices and did not hesitate to retaliate against perceived critics in a variety of unlawful ways,” Perez said. “No one in Maricopa County is above the law, and the department will fight to ensure that the promise of the Constitution is realized by everyone in Maricopa County.”

But Perez has made a priority of cracking down on police misconduct in other jurisdictions, too, noted Deborah J. Vagins, senior legislative counsel at the American Civil Liberties Union. His division has intervened against police misconduct in New Orleans and Seattle, for example.

One influential Senate Republican, Judiciary Committee ranking member Charles E. Grassley of Iowa, has raised questions about Perez’s decision-making in a separate civil rights case and has indicated it could cause problems if he is nominated to lead the Labor Department.

In that case, the Justice Department struck a deal with the city of St. Paul, Minn., in which the city withdrew from a Supreme Court lending discrimination case in exchange for the federal government agreeing not to join a pair of housing-related False Claims Act lawsuits against the city that were instigated by a whistle-blower. Republicans contend the suits had the potential to return more than $180 million in damages to the Treasury.

“It’s hard to believe that the president would nominate somebody at the heart of a congressional investigation and so deeply involved in a controversial decision to make a shady deal with the city of St. Paul, Minnesota,” Grassley said in a statement Sunday. “Not to mention the fact that he’d be handed the keys to the whistle-blower kingdom at the Labor Department. I shudder to think how whistle-blowers will be treated in the Labor Department if this quid pro quo with St. Paul is any indication of Mr. Perez’s approach to this important area of law.”

Lauren Smith contributed to this report.