Liberals resurrected their calls for filibuster reform Thursday after Senate Republicans voted to filibuster two of President Barack Obama’s nominees.

“The Senate rules must change,” said Sen. Jeff Merkley (D-OR).

In back-to-back votes, GOP senators blocked the nominations of Rep. Mel Watt (D-NC) to the Federal Housing Finance Agency and Patricia Millett to the D.C. Circuit Court of Appeals. Both were backed by a majority of senators but failed to clear the 60-vote threshold to break a filibuster. Republican Sens. Sens. Richard Burr (NC) and Rob Portman (OH) voted to advance Watt; Sens. Collins (ME) and Murkowski (AK) joined Democrats on Millett.

“Senate Republicans just blocked up-or-down votes on a judicial nominee and an executive nominee back to back, within minutes of each other,” said Merkley, a vocal proponent of filibuster reform. “This is a war on the other two branches of government and their ability to do the jobs the American people need them to do.”

“If the Republican caucus finds that despite [Millett’s] stellar legal reputation and commitment to her country that somehow a filibuster is warranted, I believe this body will need to consider anew whether a rules change should be in order,” Senate Judiciary Chair Patrick Leahy (D-VT) warned before the vote.

Sen. Tom Harkin (D-IA) also called for scrapping the filibuster after the two cloture votes.

“The lessons over this summer’s Senate rules battle should be clear,” said Fix The Senate Now, a coalition of liberal advocacy groups pushing to scale back the filibuster. “As Senate Majority Leader Reid pledged, Democrats must be prepared to change the Senate rules should Republicans continue to block these qualified nominees from receiving an up-or-down vote. If Republicans continue with their obstruction, Senator Reid must live up to his threat to change the Senate rules.”

“It forces back open the discussion about rules reform in the Senate,” said Doug Kendall, the president of the Constitutional Accountability Center, a liberal legal advocacy group.

But Republicans aren’t taking the threats of filibuster reform seriously, after Democrats raised the threat twice in the past year, only to stop short of changing the rules both times.

“Look, at the end of the day, if you’re going to bring up the nuclear threat every time something comes up, people say, ‘Bring it on.’ Go ahead. Go ahead,” said Sen. Bob Corker (R-TN). “If they want to do it, let them do it. I mean, you can do that once or twice… But at some point, you kinda have to say, look, if you want to, just go ahead and do it. I mean, if that’s what you want to do, do it. I don’t think they will.”

“If they’re going to do that, then they have the opportunity to do that,” Sen. John Boozman (R-AR) told TPM, when asked about filibuster reform. “The only problem is that the Senate will not always be controlled by Democrats. … I think that’s why it hasn’t been done in the past, because both sides realize that this is something that would be used against them.”

Republicans are especially dubious that Democrats would eliminate the blocking tool for judicial nominees as they threaten a mass filibuster of any nominee to fill three vacancies on the D.C. Circuit, a powerful court that is one notch below the Supreme Court.

“I would be shocked,” Corker said. “I just don’t see that happening. I don’t think any of them would like to see a Republican president in 2016 have a 51-vote right to have another Justice Scalia or somebody else on the Supreme Court. I don’t see that happening. I don’t think there’s anybody in our caucus that takes that seriously. … At some point there will be a Republican president.”

Earlier on Thursday, Obama’s third and final D.C. Circuit nominee, Robert Wilkins, cleared committee the Judiciary Committee by a party-line vote of 10-8. Cornelia “Nina” Pillard was approved by the panel last month. Republicans want to eliminate all three vacant seats.

“I believe that the caseload doesn’t warrant filling this position,” Sen. Kelly Ayotte (R-NH) told TPM of the D.C. Circuit vacancy, after voting to filibuster both Millett and Watt.

Corker predicted the two sides would come to a solution on the D.C. Circuit fight.

“I think at the end of the day what ought to happen is there ought to be a sit-down negotiation on the right amount of judges to be in the DC Circuit. I have suggested that to the White House. To me, ultimately, that’s what’s going to happen,” he said. “I think there’s probably a solution somewhere in between what’s being requested and where we are that probably makes sense.”