Senate Majority Leader Harry Reid issued an ultimatum to Republicans on Monday to confirm at least seven presidential appointees or face a controversial rule change that could drain their power.

Reid made the demand during a speech Monday morning to the liberal-leaning Center for American Progress, ahead of a possible showdown vote on Tuesday.

At issue is the Senate’s own rulebook, which to lawmakers is a very serious topic. Reid is threatening to flout the normal process in order to change the rules so that key presidential nominees can be confirmed with just 51 votes — as opposed to 60. In short, the move would curb the minority party’s ability to filibuster nominees.