THE REWRITING of filibuster rules by Senate Democrats on Thursday changed the legislative body in fundamental ways, and for the worse. Republicans whose unjustified recalcitrance provoked the change should be ashamed. Democrats who are celebrating will soon enough regret their decision. The radical action, a product of poisonous partisanship, will also be an accelerant of poisonous partisanship.

Fed up with Republicans repeatedly blocking President Obama’s judicial nominees to the U.S. Court of Appeals for the District of Columbia Circuit, Democrats triggered the so-called “nuclear option.” In violation of long-standing precedent, they voted by a bare majority to alter the rules of the Senate, giving the minority no voice in the procedural change. The new rule bans filibusters of presidential nominations except those for the Supreme Court.

The Democratic majority was justified in its grievance but not in its rash action. Republicans had made increasing use of the filibuster to block presidential appointments for which a majority, but not the required 60 votes, could be mustered. Most recently, they rejected three of Mr. Obama’s nominees to the D.C. Circuit without even considering their merits. Their motivation was to prevent the president from making the court more liberal. Their pretext was that the court is under-worked. As we wrote previously, their motivation was unjustified; an elected president is entitled to nominate judges who, if qualified, should be confirmed. Their rationale, if genuine, should have been satisfied by changing the size of the court in the next presidential term.

Both parties have been guilty of delaying and blocking qualified judicial nominees of presidents from the opposing side, particularly for this important appeals court. We believe a filibuster should be rarely invoked. But now that it is not an option, the result is likely to be that the partisanship of Congress will seep increasingly into the judiciary, as presidents feel no obligation to search for balance or moderation in their nominations. As Sen. Charles E. Grassley (R-Iowa) warned before Thursday’s vote, “When we have the majority, when we have a Republican president, we put more people like Scalia on the court.”

The impact of changing the rules in this way may be even more far-reaching. The Democratic action sets a precedent that a future Republican majority will use to change procedures when it gets into a political jam, rather than negotiate with Democrats. The logical outcome is a Senate operating more like the House, with no rights for the minority, no reason for debate and no incentive to cooperate. For those who view that as an improvement, we offer today’s House as a counterargument.

Democrats understood all this very well when they were in the minority. “You may own the field right now,” then-Delaware Sen. Joseph R. Biden Jr. (D) said in 2005, when Republicans threatened to invoke the nuclear option. “But you won’t own it forever. And I pray to God when the Democrats take back control we don’t make the kind of naked power grab you are doing.” Republicans resisted pushing the nuclear button then; both parties should have stepped back and hammered out a bipartisan compromise reform now.

This time Republicans proved incapable of exercising their minority rights in a responsible way. Majority Leader Harry M. Reid (D-Nev.) proved not enough of a leader to resist the “naked power grab.” American democracy is that much poorer as a result.

Read more on this topic:

Eugene Robinson: Democrats were forced to go ‘nuclear’

Jennifer Rubin: Republicans should return the favor when in power

Jonathan Bernstein:A significant change to how the nation is governed

James Downie: Republicans have only themselves to blame

The Post’s View: Judicial nominees face unfair hurdles in the Senate

Harold Meyerson: A good case against the filibuster