AP EXPLAINS: What is the Senate's 'nuclear option'?

Senate Republicans and Democrats appear to be on collision course over President Donald Trump's nominee to the Supreme Court and whether to changes Senate rules to get him confirmed.

The pressure is on Majority Leader Mitch McConnell, R-Ky., to change the parliamentary rules for Supreme Court nominees, lowering the threshold to a simple majority.

In 2013, Democrats were in the majority under the leadership of Sen. Harry Reid of Nevada and upset about the blockage of President Barack Obama's nominees to a powerful appellate court.

[...] a rules change on Supreme Court nominees would be a momentous change for the Senate, which traditionally operates via bipartisanship and consent from all senators.

Cloture — the procedural motion to end a filibuster — was attempted for the first time on a nominee in 1968 after President Lyndon Johnson tapped Abe Fortas as chief justice of the U.S., according to the Congressional Research Service.