GOP senators are starting to refer to the position that section 4 of the 14th amendment means that the president does not need congress to raise the debt ceiling as the "nuclear option." previously, the phrase "nuclear option" referred to a procedural tactic that would eliminate the filibuster in the senate by having it declared to be unconstitutional. that tactic has been much discussed but never actually used.
the reason people started referring to the elimination of the filibuster as the "nuclear option" is that opponents claimed that if anyone ever used it to eliminate the filibuster it would so poison relations between the two parties that nothing would ever get done again in the senate. it was "nuclear" in the sense of "mutually assured destruction." like with MAD, the threat of completely ending the senate's ability to function was viewed as so horrible as to deter anyone from actually trying it.
by applying the nuclear metaphor to the debt ceiling context, are the republicans now implying that if president obama decided the debt ceiling is unconstitutional that would also end all cooperation between the parties? if so, is that really much of a threat? congress is already pretty disfunctional. there doesn't seem to be much cooperation to lose..