Senate majority leader Harry Reid has announced he'll use the "nuclear option" to push through filibuster reform if Republicans don't agree to a deal within the next 24-36 hours.
The so-called nuclear option - or "constitutional option" - allows the Senate to reform its own rules with a simple majority of 51, rather than with a supermajority of 60. Reid says he has 51 Democratic votes, so he could reform - or end - the filibuster without any Republican support at all.
The nuclear option has never been used before, and it's not set out in the Senate's rules. The only warrant for using it comes from a 1957 opinion written by then-Vice President Richard Nixon.
Reid also said Tuesday that he's in talks with Senate minority leader Mitch McConnell, in hopes of working out a bipartisan filibuster deal.