Republican senators, White House aides argue, have developed what amounts to a silent filibuster, using the “blue slip” tradition that gives home state senators signoff power for in-state nominees. Given the number and length of delays, they say trying to collaborate on nominations has become an unbearable burden, the blue slip an outdated courtesy — there are 53 pending judicial nominees, and only six of the 37 vacancies without a pending nominee are in states with two Democratic senators.

Meanwhile, the White House points to examples like GOP Sens. Marco Rubio of Florida and Richard Burr of North Carolina, who refused to return blue slips on nominees they recommended, or people like former Missouri Supreme Court Justice Ronnie White, whose nomination to the federal bench by Obama is still waiting on a blue slip four months after Sen. Roy Blunt (R-Mo.) said he would return it.

“The blue slip system acts as a constraint, and a very significant constraint — and more so than the filibuster, on the president’s choices of potential nominees,” said Ruemmler, who oversees nominations for President Barack Obama. It’s a policy “that assumes a level of good faith on behalf of the Republican senators.”