Under his watch, the Justice Department Civil Rights Division has conducted a record 17 investigations of police and sheriff departments – among the most famous of them the office of Arizona’s Sheriff Joe Arpaio.

And in the most high-profile cases – where the Justice Department has charged discrimination against Latinos and immigrants –Thomas Perez has been front and center.

The fight for the underdog has made Perez, assistant U.S. attorney general for civil rights and rumored to be the person President Obama is considering nominating to be Secretary of Labor, a hero to civil rights advocates, but a liberal attack dog to conservatives.

“He likes to fight for those who don’t have the ability to fight for themselves,” said A.J. Bellido-de Luna, managing director of the University of Maryland Law School clinical law programs. “In my opinion, that was his greatest gift.”

Bellido-de Luna got to know Perez, who grew up in Buffalo, N.Y. to Dominican parents, when he was a law student at the University of Maryland and Perez was director of the clinical law programs more than a decade ago.

“One of the things he disliked greatly, and there are cases of it, was police taking liberties they shouldn’t take, or taking away others’ liberties,” said Bellido-de Luna, who was a Maryland police officer before becoming a lawyer. “He has absolute trust and respect for the police and the difficulty of their job, what he doesn’t have any patience for is when police cross the line.”

Perez, 51, has gone after states, like Arizona and Alabama, which have enacted their anti-illegal immigration laws, arguing that that they are encroaching on what is purely a federal responsibility. He argued on behalf of the U.S. Dept. of Justice against Arizona’s well-known immigration law, known as SB 1070, before the U.S. Supreme Court.

Critics say he was pushing amnesty and trying to interfere with state rights.

"Under his leadership, the civil rights division has been on the other side of the rule of law when it comes to election integrity and immigration enforcement,” said Tom Fitton, president of Judicial Watch, a conservative government watchdog group in Washington, D.C. “He’s attacked states that are trying to establish law on immigration matters, voter ID and other security measures.”

Fitton didn't mince words as to what he sees as Perez's partisan political agenda.

“He’s a hardcore left-wing activist,” Fitton said, “who I think is being tapped for that reason.”

Perez's nomination to the Labor Department could come as early as Monday, people familiar with the process told reporters. They spoke on condition of anonymity because the official announcement has not yet been made.

White House spokesman Matt Lehrich declined to comment.

Perez has led the Justice Department's Civil Rights Division since 2009 and previously served as Maryland's labor secretary. He is expected to have solid support from organized labor and the Hispanic community, which is eager to have Hispanic representation in Obama's cabinet.

Perez was the first Latino elected to the Montgomery County Council in Maryland, where he served from 2002 to 2006. If confirmed, he would replace Hilda Solis, who resigned in January to return to her native California. He has spent his career in public service since graduating from Harvard Law School.

Perez is a first-generation Dominican-American who, according to published reports, became a supporter of labor unions after a Teamster who had lost his job became a surrogate father to him when his own father died of a heart attack. It is said that Perez, who was 12 when he lost his father, never has forgotten the help the Teamster and the union extended to Perez after the loss.

Cid Wilson, a Wall Street financial analyst and advocate for Latino affairs, said that Perez, with whom he often interacted, “would be an outstanding, history-making Labor Secretary.”

“He understands the importance of developing a workforce,” Wilson said. “He has that overall understanding that we will build a strong economy by building the middle class.”

Bellido-de Luna believes that Perez can help bring bipartisan consensus to labor issues.

“He’s the kind of person who would pay attention to every single detail,” he said, recalling Perez’s days at the University of Maryland. “He would listen to all sides, to everybody, and would try to figure out what the best solution was. He’s a real consensus builder.”

But his aim was not to make everyone happy, he added.

“The last thing he wants to do is to have to litigate anything,” Bellido-de Luna said. “But he’s intelligent, he knows how to go after someone or a group if he has to. You don’t want to be the person who has done something wrong and then has to face him.”

The Associated Press contributed to this story.

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