All eight Republicans on the Senate Environment and Public Works Committee refused to show up Thursday for a vote on President Obama's pick to head the Environmental Protection Agency, stalling the confirmation process and raising the possibility that the GOP will hold up the nomination indefinitely.

The boycott prevented the committee from holding a vote on nominee Gina McCarthy that would have moved the debate over her appointment to the full Senate. Committee rules require a majority of members to be present, including at least two from the minority party, to hold a vote.

Republicans, led by the committee's ranking member, Sen. David Vitter (R-La.), said they weren't prepared to vote just yet because the EPA had been "stonewalling" their requests for more transparency.

"These requests are all about openness and transparency and things required by present law,'' Vitter said. "We're not asking the Obama administration to walk away from their views about carbon or anything else. We are asking for openness and transparency and we are asking that present law be followed in a full and fair and reasonable way.''

Democrats on the committee said they were given only a half-hour's notice that their Republican counterparts wouldn't be appearing for the vote on McCarthy, who is currently the in charge of the EPA's office of air and radiation. Democrats uniformly condemned the tactic, charging that Republicans were interested only with "obstructionism," and not with getting answers.

"We know they don't want answers to questions," Sen. Tom Udall (D-N.M.) said of the boycott. "They just haven't showed up."

The committee's chairwoman, Sen. Barbara Boxer (D-Calif.), called the delay "unacceptable," noting that the Senate had confirmed McCarthy to her current EPA post just four years ago. The delay was also troubling, she said, because she'd never seen a cabinet nominee face so many questions during a committee confirmation hearing.

According to the Washington Post's Darryl Fears, McCarthy was asked to answer well over 1,000 questions from committee members — far more than other EPA nominees in recent years.

From the Washington Post

In the weeks-long hearing on her nomination, McCarthy took more than 1,100 questions, more than 1,075 of which came from Republicans. A single conservative, Sen. David Vitter (R-La.), asked 600 of them, according to the majority office of the committee.

By contrast, the EPA’s former administrator under Obama, Lisa P. Jackson, took 157 questions, 118 from Republicans. President George W. Bush’s nominees to lead the agency, Stephen L. Johnson and Michael O. Leavitt, took 230 and 305 questions, respectively, according to a Democratic official who spoke on the condition of anonymity because the nomination was still pending. [Washington Post]

Should the committee ultimately hold a vote to advance McCarthy on to the full Senate, it's uncertain if lawmakers there would approve her appointment. Vermont Sen. Bernie Sanders (I) said on Thursday that Democrats lacked the 60 votes necessary to break a GOP-led filibuster, an obstacle that he said seemed like a real possibility at this point. A spokesman for Senate Minority Leader Mitch McConnell (R-Ky.) hinted that a filibuster was being considered when questioned by Politico, saying, "Let's see how the Obama administration responds to this reasonable request."

Arkansas Sen. John Boozman (R) was more direct, telling reporters on Wednesday, "I think everything's on the table." 

It's the second time this week that Republicans have held up one of Obama's cabinet choices. On Wednesday, Republicans blocked a confirmation vote on Thomas Perez, Obama's labor secretary pick, by threatening to prevent the Senate Health, Education, Labor, and Pensions Committee from even convening a meeting.

White House Press Secretary Jay Carney on Thursday pleaded with the GOP to stop "gumming up the works" on the president's cabinet picks, who he said are "enormously qualified" for their jobs.