Sen. David Vitter, R-La., announced Monday that he will block President Barack Obama’s nominee for Labor secretary, Thomas E. Perez, until he receives more information about Perez’s enforcement of a federal voting law as the head of the Justice Department’s Civil Rights Division.

The announcement, made less than two hours after Obama nominated Perez to lead the Labor Department, indicates that another of the president’s high-level nominees could face a protracted confirmation fight in the Senate this year. Obama’s choices to lead the Pentagon and CIA, Chuck Hagel and John O. Brennan, also faced strong Republican opposition — including filibusters — before ultimately being confirmed.

Some other Senate Republicans, however, took a more measured approach to Perez, indicating that the caucus may still be evaluating how forcefully it will object to the nomination. If confirmed, Perez would become the only Latino member of Obama’s second-term Cabinet, and Republicans may be uneasy about vocally opposing Perez after handily losing the Latino vote in last year’s presidential election.

Through a spokesman, Vitter said he would allow Perez’s nomination to proceed only if Attorney General Eric H. Holder Jr. responds to a letter Vitter sent him in November 2011. In that letter, Vitter raised questions about what he called the Justice Department’s “selective enforcement” of the National Voter Registration Act, a 1993 federal law intended to streamline the voter registration process in the states.

Vitter said he is troubled by reports that the department — and, specifically, Perez’s division — aggressively enforced one aspect of the law that encourages welfare recipients to become registered voters while doing little to enforce a separate section of the law that is intended to prevent ineligible voters, such as convicted felons, from being registered.

“The two provisions act together as counterparts, but it is evident that the Justice Department is not enforcing them equally,” Vitter wrote.

“Justice must fully enforce this law, rather than refusing to enforce the voter list integrity provisions while making the welfare agency registration law its top priority,” he continued. “The Civil Rights Division does not have the right to pick and choose which laws are worthy of enforcement and which ones are not. I urge you to personally ensure that the Justice Department does not enable voter fraud by neglecting to enforce Section 8 of the NVRA.”

Vitter’s announcement seemingly ensures that Holder must again provide a written answer to a Republican senator before one of Obama’s Cabinet nominees can be confirmed.

Brennan’s confirmation to head the CIA moved forward only after Holder provided a written clarification to Sen. Rand Paul, R-Ky., about the administration’s policy on lethal drone attacks in the United States. Paul led a nearly 13-hour talking filibuster on the Senate floor in a successful effort to obtain Holder’s response.

Other Republicans Wait and See

Vitter was not the only Republican on Monday who announced immediate opposition to Perez. GOP Sen. Jeff Sessions of Alabama, a member of the Judiciary Committee, unequivocally called Perez “the wrong man for this job” and cited the nominee’s views on immigration and his often controversial tenure at the Justice Department.

“This is an unfortunate and needlessly divisive nomination. The top priority of the secretary of Labor should be to create jobs and higher wages for American workers. But Mr. Perez has aggressively sought ways to allow the hiring of more illegal workers,” Sessions said in a statement. “Mr. Perez has also had a controversial tenure at the Department of Justice where he has demonstrated a fundamentally political approach to the law.”

But even as Vitter and Sessions highlighted the deep GOP uneasiness about Perez, the top Republican on the panel that will hold hearings on the nomination said he would keep an open mind.

“I look forward to meeting with Mr. Perez and examining his record and qualifications,” Sen. Lamar Alexander of Tennessee, the ranking member of the Health, Education, Labor and Pensions Committee, said in a statement. “Any nominee for this position should be ready and able to work with both parties in Congress to make it easier for the private sector to create good jobs for the 12 million workers still unemployed now, three and a half years after the recession ended.”

Alexander is one of nine current Republican senators — and 17 overall — who voted for Perez when he was confirmed as the Civil Rights Division head in October 2009. Perez was confirmed by a vote of 72-22.

HELP Chairman Tom Harkin, D-Iowa, said he hopes to begin the vetting process quickly.

“I pledge to work with ranking member Alexander and members of the committee to promptly complete our review of Mr. Perez’s nomination,” Harkin said. “Mr. Perez brings significant experience and expertise to this position, and I am confident that he will serve ably if confirmed.”

Perez previously served 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.

Labor Unions Supportive

Labor unions and liberal advocacy groups praised Obama for nominating Perez, citing his record at the Civil Rights Division as a benefit, not a liability.

Mary Kay Henry, president of the Service Employees International Union, lauded Perez’s recent work, making a veiled reference to the racial profiling charges he pursued against Joe Arpaio, the Republican sheriff of Maricopa County, Ariz., who is among the most divisive figures in the national immigration debate.

“During his time at the Justice Department, Mr. Perez has initiated many important challenges to state and local laws that sought to infringe on the civil rights of minority communities,” Henry said.

Indeed, immigration could become a key focus of Perez’s tenure at Labor if he is confirmed, and many pro-labor stakeholders highlighted that on Monday. Perez, whose parents emigrated from the Dominican Republic, opened and closed his brief nomination acceptance speech at the White House in Spanish.

“The appointment of Thomas Perez as head of the Department of Labor brings immigrants one step closer to equal rights at the workplace,” said Pablo Alvarado, executive director of the National Day Laborer Organizing Network. “It is a signal of the need for full labor protections within immigration reform.”

Richard Trumka, president of the AFL-CIO, also noted the qualities Perez would bring to the immigration debate.

“In the 1990s, he worked on the front lines of the effort to pass comprehensive immigration reform under the leadership of the great Sen. Ted Kennedy — a job that will serve him well in today’s drive for commonsense immigration reform,” Trumka said.

Business-oriented stakeholders, meanwhile, took a wait-and-see approach, similar to Alexander’s.

“The Department of Labor handles many issues of importance to employers and employees, and it is our hope that Mr. Perez will work with the business community to advance policies that promote jobs and economic growth,” said Randy Johnson, the senior vice president of Labor, Immigration and Employee Benefits at the U.S. Chamber of Commerce.

“From our point of view, he’s no worse than the rest,” said Fred Wszolek, spokesman for the anti-labor Workforce Fairness Institute. “He will be strongly pro-labor and will push union bosses’ agenda, and we assume he’ll do that just fine. But we’re just happy it’s not a nominee like Richard Griffin.”

Obama appointed Griffin, a former union official, along with Sharon Block to the National Labor Relations Board while the Senate was on holiday break in January 2012. Both appointments were recently ruled invalid by the U.S. Court of Appeals for the District of Columbia.

“The standard used to be the appearance of his propriety,” Wszolek said. “There doesn’t seem to be that kind of issue with this nomination.”