For 100 years the Senate has allowed home-state senators to play a central role in approving nominees for federal judgeships in their states.
In order for a judicial nomination to move forward, both senators from a nominee's state must return a "blue slip" that signals their agreement that that nominee should receive a hearing in the Judiciary Committee.
The blue-slip process was put in place to ensure judges nominated by the president are mainstream and well-suited to the state in which they would serve - not handpicked by special-interest groups based in Washington.
Republicans have long been on board with this tradition. In 2009, the entire Republican conference wrote to President Barack Obama, telling him they had to be consulted and would use the blue-slip process to block any nominees from their home states they didn't approve of.
Both parties have defended the blue slip to ensure senators play a role in selecting judicial nominees. Up until now.
Senate Republicans are threatening to eliminate the blue slip, the last remaining tool that ensures home-state senators of both parties play a role in the process of appointing judges.
Despite using the blue slip to block the nomination of Kentucky Supreme Court Justice Lisabeth Tabor Hughes to the U.S. Court of Appeals for the 6th Circuit, Senate Majority Leader Mitch McConnell, R-Ky., is leading the charge.
He has now reversed the position he held during the Obama administration, arguing that the blue slip should be treated as a "notification" of how a senator intends to vote, even though Republicans used it to block nominees.