Thomas E. Perez, the Marylander nominated by President Barack Obama to lead the U.S. Department of Labor, is set to face a critical vote in the Senate this week that puts his confirmation in the middle of a blistering battle over the use of the filibuster.

Four months after his nomination, the 51-year-old Takoma Park man is one of seven presidential appointees whom Democratic leaders plan to bring to the Senate floor as early as Tuesday.

It is unclear whether Perez, whom Senate Republican Leader Mitch McConnell has called a "crusading ideologue," can get the 60 votes needed to overcome a filibuster and win confirmation. Democrats hold a 52-46 majority in the Senate, and the body's two independents usually vote with them.

The votes scheduled Tuesday to end debate on the seven nominees come amid a deeply partisan fight over whether the GOP minority has abused its power to delay confirmations through the use of the filibuster. Democrats have threatened to limit delays of executive branch nominees through a controversial procedure to change Senate rules known as the "nuclear option."

As the votes neared and the rhetoric sharpened, the 100 senators held a rare closed meeting Monday in the Old Senate Chamber, the ornate room in the Capitol in which the body met from 1819 until 1859.

A bipartisan group of senators, meanwhile, began negotiations to keep Democrats from pursuing rules changes that could have far-reaching consequences for the body. Some lawmakers who emerged from the meeting late Monday said they were optimistic a deal could be reached — eventually.

"At the end of the day, we didn't come up with a solution," said Sen. Dick Durbin of Illinois, the No. 2 Democrat in the Senate. "The conversation will continue."

Perez, the only Hispanic nominated to Obama's second-term Cabinet, headed the Maryland Department of Labor, Licensing and Regulation during the first term of Gov. Martin O'Malley.

He was the first Hispanic to win a seat on the Montgomery County Council in 2002 and ran briefly for Maryland attorney general in 2006.

Sen. Tom Harkin, the Iowa Democrat who chairs the Senate committee that advanced Perez's nomination on a party-line vote in May, asked why the confirmation should require a supermajority to pass.

"Why should it take 60 votes?" he asked. "Why shouldn't it be a majority vote, up or down?"

Democrats say Perez is well qualified for the labor job and has a record of bipartisanship. Republicans counter that the Justice Department's Civil Rights Division made a series of partisan decisions under his leadership and say Perez has not been entirely forthcoming about his role in those decisions.

Perez is one of several Obama nominees who have waited months for confirmation. Democrats are also looking to end debate on Richard Cordray to lead the Consumer Financial Protection Bureau, three members of the National Labor Relations Board and Gina McCarthy, whom Obama nominated to lead the Environmental Protection Agency in March.

Senate Majority Leader Harry Reid threatened to end filibusters on executive branch nominations if Republicans do not allow an up-or-down vote on seven appointees, including Perez.

"The power of an extreme minority now threatens the integrity of this institution," Reid said in a speech Monday at the liberal Center for American Progress. "My efforts are directed to save the Senate from becoming obsolete."

Under the so-called nuclear option, Democrats would execute a series of procedural moves on the floor to change Senate rules with a simple majority — meaning Democrats could make the change without GOP support — rather than the two-thirds vote usually required.

Reid has described the potential impact as insignificant. But Republicans say it could fundamentally change the way the Senate does business, and Democrats objected when Republicans considered a similar move when the GOP held the Senate majority and George W. Bush sat in the White House.

Republicans have expressed concern that if Democrats changed the rules for nominations, they could then pursue a similar effort to limit filibusters on legislation as well.

"The rule change that is being considered this week is more far-reaching and more significant than has been advertised," said Sen. Jeff Flake, an Arizona Republican. "It is a big deal. It has the potential to change this institution in ways that are both hazardous and unforseen."

A bipartisan group of lawmakers led by Sen. John McCain was working late Monday to head off the potential rules change. McCain, also an Arizona Republican, was a member of the Gang of 14 lawmakers that successfully staved off the GOP proposal to invoke the nuclear option in 2005.