The Senate Republican leadership threw its weight behind Federal Election Commission nominee Hans von Spakovsky on Wednesday, threatening to bring the confirmation process to a standstill and testing Democrats’ will to block to the controversial GOP pick.

“I just want to assure everyone that all [FEC] nominees will move together on the floor or not at all,” Senate Minority Leader Mitch McConnell (R-Ky.) told the Senate Rules and Administration Committee, which agreed Wednesday morning to send the nominations of Republicans von Spakovsky and David Mason and Democrats Steven Walther and Robert Lenhard to a full Senate vote.

At Wednesday’s committee hearing, Republicans voiced their concerns over what they called a long-standing agreement to ship FEC nominees to the Senate floor in pairs, a deal Sen. Saxby Chambliss (R-Ga.) said Democrats would be wise to honor.

“I think we’re breaking precedent in a way that’s going to cause problems for this committee down the road. I understand the objections to the individual … but Democrats have a right to make their nomination and Republicans have a right to make their nomination,” Chambliss said. “That’s the way it’s always been and that’s the way I hope it’s going to be in the future.”

McConnell, whose appearance at Wednesday’s meeting was unannounced, is a former chairman of the Rules panel and a veteran of FEC confirmation brinkmanship. Seven years ago, Democratic concerns over another controversial Republican pick, Bradley Smith, prompted threats by McConnell to block Democratic nominee Danny Lee McDonald.

Both eventually were confirmed by separate votes.

“There obviously, from time to time, have been nominees on both sides that were, shall I say, not enthusiastically embraced by the other side,” McConnell told the panel. “The Federal Election Commission was set up on purpose to be a 3-3 agency, so that neither political party would yield to the temptation to try and take advantage of the other.”

McConnell’s promise not to blink on von Spakovsky’s nomination marks the first time Senate GOP leadership has given a firm indication that it will back the controversial former Justice Department official.

Von Spakovsky and three colleagues are serving recess appointments that expire at the end of the year. Already one Republican member short, the six-person panel must have four commissioners present to conduct business, a quorum that may not be met if Democrats force an indefinite standoff with McConnell, who may choose to filibuster Democratic nominees in protest.

But after months of pressure by liberal activists and civil rights groups over the nomination, Senate Democrats may face an uncomfortable decision of shutting down the commission during an election year or alienating their base. While at the Justice Department, critics argue that von Spakovsky pushed controversial voting laws disenfranchising minorities and worked aggressively to politicize the agency.

Von Spakovsky, who worked for Bradley Schlozman — another White House operative placed at the Justice Department — maintains he was merely the “face that [DOJ employees] saw.”

“When the president of an organization makes a decision on a matter, he’s not the one that goes down and tells the guys on the assembly line. The president tells the senior vice president, who tells the vice president, who tells the manager. And it’s the manager who goes and delivers the message to the line people,” von Spakovsky testified before the Rules panel earlier this summer. “When the assistant attorney general made a decision … [he] wasn’t the one who would call and talk to the chiefs, deputy chiefs or the line attorneys on a case; they would tell me what the decision was on a matter.”

But Rules Chairwoman Dianne Feinstein (D-Calif.) said at Wednesday’s hearing that she’s seen plenty of evidence that von Spakovsky was a principal in partisan antics at the Justice Department, which should preclude his further service on the commission.

“I’ve been through the Judiciary Committee investigations,” Feinstein said at Wednesday’s hearing. “I believe he’s not an unbiased individual,”

Campaign finance reform activists criticized McConnell’s warnings Wednesday, arguing that Republicans are hoping to use precedent as an excuse to anonymously support a controversial White House pick. While reformers agree pairing nominees is the norm, there have been exceptions.

“This is a false claim,” Fred Wertheimer, president of Democracy 21, said of the Republicans’ argument that commissioners have never been confirmed individually. “In the case of Brad Smith and Danny McDonald there were individual votes. The effort is being made here to have a bloc vote so there is no individual accountability on where Senators stand.”

The Campaign Legal Center’s J. Gerald Hebert said Wednesday’s proceedings “show that no nominee’s partisan record of misdeeds is enough to derail their nomination to the FEC” and is evidence that legislative oversight of the agency is broken.

“The confirmation process has been shown to be as dysfunctional as the agency itself and today’s disappointing events lay bare the desperate need to replace the FEC with an independent entity not ‘run’ by party marionettes,” Hebert said.