Exactly how the debate over filibusters will affect Perez remains unclear. GOP leaders have acknowledged that Democrats likely have the 60 votes needed to end debate and confirm him, but no rank-and-file Republican has publicly stated support.

To secure confirmation, Perez would need six Republicans to buck their own leadership.

Republicans — and many Democrats — worry that relying on the nuclear option to change Senate rules could further poison the already hyper-partisan environment on Capitol Hill, making it more difficult for the Obama administration to advance legislation such as the landmark immigration bill that cleared the Senate late last month.

Republicans have raised several concerns about Perez, but have focused mainly on a deal by the Justice Department to back out of a lawsuit filed against the city of St. Paul, Minn., in exchange for city leaders dropping separate litigation against the federal government.

Republicans have said taxpayers could have recovered $200 million in misspent funds if the Justice Department had pursued the case. Perez has said he was concerned the city's lawsuit could have resulted in an adverse Supreme Court ruling. He says he cleared the move with ethics officials in the department.

Debate over Perez's confirmation has come at a politically sensitive moment for Republicans, who have been eager to court Hispanics after losing three quarters of their vote to Democrats in the 2012 election.

The bipartisan immigration overhaul the Senate approved last month, a Hispanic priority, appears to have little chance of success in the Republican-controlled House of Representatives.

Hispanic groups have strongly backed Perez to lead the Labor Department.

Perez is not new to confirmation battles. GOP lawmakers delayed a confirmation vote for his current position at the Justice Department for more than six months in 2009.

He ultimately received a bipartisan vote of 72-22.

john.fritze@baltsun.com

twitter.com/jfritze

x months in 2009.

He ultimately received a bipartisan vote of 72-22.

john.fritze@baltsun.com

twitter.com/jfritze