WASHINGTON — Senate Republicans are preparing to abolish the final vestige of power that the minority has to block Supreme Court nominations through a filibuster. Many senators in both parties now worry that the final and biggest domino — the power to filibuster legislation — will be next.

In recent years, as partisanship has escalated, the Senate has required a 60-vote majority for almost any controversial legislation to overcome a filibuster. Gone, for the most part, are bipartisan quorums that used to pass large and complex laws with simple majorities.

But as both parties have moved to do what was once unthinkable — eliminating the filibuster for judicial and cabinet nominees, known as the nuclear option — senators are now forced to consider if the final step could be in the offing, one that would fundamentally alter the character of the Senate and make it indistinguishable from the House in a crucial way.