WASHINGTON — Senate Republicans on Thursday engineered a dramatic change in how the chamber confirms Supreme Court nominations, bypassing a Democratic blockade of Judge Neil M. Gorsuch in a move that will most likely reshape both the Senate and the court.

After Democrats held together Thursday morning and filibustered President Trump’s nominee, Republicans voted to lower the threshold for advancing Supreme Court nominations from 60 votes to a simple majority.

In deploying this so-called nuclear option, lawmakers are fundamentally altering the way the Senate handles one of its most significant duties, further limiting the minority’s power in a chamber that was designed to be a slower and more deliberative body than the House.

The move, once unthinkable among senators, is a testament to the creeping partisan rancor in recent years, after decades of at least relative bipartisanship on Supreme Court matters. Both parties have warned of sweeping effects on the court itself, predicting the elevation of more ideologically extreme judges now that only a majority is required for confirmation.