Perez never forgot.

Now, Perez, 51, a first-generation Dominican American, is in line to lead the Department of Labor. President Obama plans to nominate Perez, assistant U.S. attorney general for civil rights, to be labor secretary, according to two people in the administration familiar with the decision.

White House officials declined to comment on Perez or the nominating process.

Perez has strong labor support and served as Maryland Gov. Martin O’Malley’s (D) labor secretary from 2007 until 2009, when he was tapped for the Justice Department position. Perez, a longtime Takoma Park resident, also served on the Montgomery County Council and was the first Latino elected to the council. He has been the key official under Attorney General Eric H. Holder Jr. handling civil rights cases, the centerpiece of what Holder hopes will be his legacy.

Reached by telephone Saturday, Perez said: “I can’t really discuss it, I apologize.”

Perez would replace Hilda L. Solis, who resigned in January. If nominated and confirmed, he would satisfy requests from Latino groups for representation in Obama’s second-term Cabinet.

Friends and colleagues say Perez has gained a unique perspective from working in federal, state and local government. “That is a very good range of experiences, a lot of perspective to see government at all those different angles,” said Ronald Weich, a former assistant attorney general for legislative affairs and now dean of the University of Baltimore’s law school.

But Perez’s possible nomination, which must be confirmed by the Senate, was already drawing criticism from one Republican lawmaker, Sen. Charles E. Grassley (Iowa). In a statement, Grassley said that if Perez is nominated, “he should face a lot of tough questions” about the Justice Department’s role in a decision last year by St. Paul, Minn., to withdraw a housing discrimination case that was before the Supreme Court.

On civil rights, Perez’s division oversaw voting rights cases against South Carolina and Texas. The Justice Department blocked a law in Texas last year that required voters to show a photo ID, following similar action in December 2011 to block a voter ID law in South Carolina. Both states filed lawsuits in U.S. District Court for the District of Columbia to overturn the federal action. The court struck down the Texas voter ID law and approved the South Carolina law, but ordered it delayed until at least this year.

The Civil Rights Division also conducted 17 probes of police and sheriff’s departments, the most in its 54-year history.

One of them involved America’s self-proclaimed toughest sheriff, Joe Arpaio of Arizona’s Maricopa County. The Justice department sued him, his office and the county last year for civil rights violations after months of negotiations failed to yield an agreement to settle allegations that his department racially profiled Latinos in immigration patrols.

Hilary O. Shelton, director of the Washington bureau of the NAACP, said Perez “has been one of the most irrepressible forces fighting for civil rights in decades.”

Perez has spent nearly his entire career in public service. After graduating from Harvard Law School, he clerked for a federal judge in Colorado and then worked as a prosecutor in the Civil Rights Division, handling some of the department’s most high-profile civil rights cases.

Weich, his Justice Department colleague, said he invited Perez to speak to law students recently. Asked to talk about his different jobs, Perez “spoke most passionately about his time in local government,” Weich said.

Perez once said he’d dreamed of elective office since his childhood in Buffalo, where he grew up as the youngest of five brothers and sisters.

He was teaching at the University of Maryland School of Law when he decided to run in the 2002 Democratic primary for the Montgomery council. He wooed Latino immigrants and other minorities in District 5, an increasingly diverse area spanning parts of Silver Spring, Kensington, Wheaton and Takoma Park, where Perez moved in 1995.

He became just the second minority ever to be elected to the nine-person council.

“He’s very passionate about what he believes in; he pushed his ideas very forcefully,” said Douglas M. Duncan, who was Montgomery County executive during Perez’s council stint.

Perez pushed a “bill of rights” for domestic workers, tried to toughen county laws against predatory lending and supported the expansion of medical clinics to serve the uninsured. He also fought to import cheaper prescription drugs for county employees — a plan blocked by the Food and Drug Administration.

In 2005, Perez became council president and the state’s highest-ranking Latino elected official. The following year, he entered the wide-open Democratic primary for Maryland attorney general. Labor unions and the state teachers association supported him, but he never made the ballot: The Maryland Court of Appeals ruled that the former federal prosecutor was ineligible because he lacked sufficient legal experience in the state.

“That was a really crushing experience for him,” recalled Rob Richie, a friend from Takoma Park. Richie, executive director of the voting reform group FairVote, said Perez could have gone into the private sector “to make a lot more money.”

But O’Malley appointed him Maryland’s secretary of labor, licensing and regulation. In that role, Perez pushed to protect employees from being incorrectly classified as independent contractors, a categorization that kept them from receiving unemployment insurance and workers compensation.

Fred D. Mason Jr., president of the Maryland and District of Columbia AFL-CIO, on Saturday called that Perez’s most important accomplishment in Annapolis.

“As a union leader, I certainly believe that labor rights and workers’ rights are also civil rights, and Tom has an appreciation for that,” said Mason, who represents about 350,000 workers.

Duncan, the former county executive, called Perez “a fierce advocate of labor.” He was also extremely loyal to O’Malley, Duncan said, recalling that Perez surprised some of his liberal allies by supporting the governor’s proposal to legalize slot-machine gambling in Maryland.

“He is someone who understands the plight of people in different positions,” said Isiah Leggett, the Montgomery county executive and former council member. “He also has the ability to bring practical and intellectual honesty to issues. You often don’t find that caliber of person who has served at the local level.”

When Leggett, the only African American ever elected to the county council, announced his campaign for county executive, Perez was among the first to endorse him.

O’Malley administration officials declined to comment on rumors that Perez might be Obama’s choice to head the Labor Department.

Perez received his undergraduate degree from Brown University in 1983, and four years later received law and public policy degrees from Harvard University. His wife, Ann Marie Staudenmaier, is an attorney with the Washington Legal Clinic for the Homeless.