Republicans are threatening a mass blockade of President Barack Obama’s three most important judicial nominees ahead of an expected Thursday vote on the first of them.

Backed by House colleagues and GOP attorneys general from around the country, Senate Republican leaders are whipping opposition to advancing the nomination of Patricia Millett — or anyone else — for the D.C. Circuit Court of Appeals, which is one notch below the Supreme Court and often has the final word on matters of executive authority.

“This week, Sen. Reid has teed up President Obama’s court-packing plan for the D.C. Circuit Court of Appeals, a court that some people call the second most important court in the nation,” Senate Minority Whip John Cornyn (R-TX) told reporters. “The last thing we need to do when money is tight … is throw more money at unneeded judges on this court, in an attempt to simply pack the court in order to tilt that court ideologically in a way that favors the big government agenda of the Obama administration.”

“We intend to stop it,” he said.

Cornyn’s court-packing claim is misleading — it is a reference to President Franklin Delano Roosevelt’s attempts to expand the size of the Supreme Court; Obama merely wants to fill vacancies on the appellate level. But he repeated the talking point in multiple op-eds recently, laying the groundwork for a mass filibuster and pressuring GOP senators not to allow Obama to fill any of the three vacant seats on the D.C. Circuit court.

“I can’t think of anything more ridiculous,” Senate Majority Leader Harry Reid (D-NV) said Wednesday. “Making nominations to vacant judgeships is not court-packing. It’s the president’s job.” Talking up Millett’s qualifications as a Supreme Court litigator and her integrity, he said, “It is truly a shame that Republicans would filibuster this exceedingly qualified nominee for unrelated political reasons.”

The Senate is scheduled to hold a cloture vote on Thursday to move the Millett nomination forward. Democrats have vowed to fight to confirm her, but it’s not clear they have the necessary five Republican votes to get to 60 and break a filibuster. (Cory Booker is expected to be sworn in on Thursday and give Senate Democrats a 55th member.)

Republicans don’t take issue with Millett’s qualifications; they argue that the court’s caseload is relatively low and so the size of its active bench should be reduced from 11 to eight judges. If they refuse to relent, it would put Democrats in a difficult position, forced to either surrender on a top judicial priority or possibly threaten to scale back the filibuster.

Reid won’t go there, for now at least. “I’m not going to talk about hypotheticals,” he told reporters. “I don’t know why anyone would vote against her.” Even if he wanted to get rid of the filibuster for judges, it’s not clear a majority of Democrats would support him. Some are hesitant to surrender their ability to block future judicial nominations. But a GOP blockade of three top nominees may bring about pressure — and political cover — to consider that option.

Republicans aren’t fretting. “I don’t really take this threat of the nuclear option very seriously when it comes to judicial nominations,” Cornyn told reporters.

The D.C. Circuit is the GOP’s silent weapon against Obama’s use of executive authority to achieve progressive goals where Congress won’t act. The conservative-leaning court has invalidated multiple actions by the Obama administration on issues like environmental protection, labor regulation and recess appointments. And the GOP base is determined to have a judiciary that favors their ideological goals — more so than the progressive base.

Reid accused Republicans of hypocrisy for saying the court has been under-worked and doesn’t need more than eight active judges, pointing out that they’ve voted to confirm additional judges to the bench under previous GOP presidents.

“Senate Republicans were happy to confirm judges to the D.C. Circuit when Presidents Reagan and George W. Bush were in office. But now that a Democrat serves in the White House, Republicans want to eliminate the remaining three vacant D.C. Circuit Court seats, although the court’s workload has actually grown since President Bush was in office,” he said. “Republicans are using convenient but flawed political arguments to hamstring this vital court and deny highly qualified nominees like Ms. Millett a fair up-or-down vote.”