In a shocking development Thursday evening, Senate Majority Leader Harry Reid (D-Nev.) triggered a rarely used procedural option informally called the "nuclear option" to change the Senate rules.

Reid and 50 members of his caucus voted to change Senate rules unilaterally to prevent Republicans from forcing votes on uncomfortable amendments after the chamber has voted to move to final passage of a bill.

Reid's coup passed by a vote of 51-48, leaving Senate Republican Leader Mitch McConnell (R-Ky.) fuming.