She announced her intention to resign, but said she woud stay seated until a replacement was confirmed.
I know that.
But how can the Senate confirm a justice when there is no vacancy?
I'm speaking theoretically. Just because she said she will resign doesn't mean she's bound to do so.
She didn't say "confirmed by the Senate," or other language such as "advice & consent."
I think one can make the straight faced argument that "confirmed" includes the power vested in the President to fill up all Vacancies that may happen during the Recess of the Senate. IOW, the Presidential confirmation creates the vacancy.
Still, it's merely academic in this case, certainly at this point in time. The President has shown appropriate deference to the Senate with regard to making recess appointments, always giveing the Senate reasonable time to act on the nomination before he implements a recess appointment. I would not be against threats and use of the recess appointment power if the Senate engaged in cloture abuse in order to avoid voting on a SCOTUS nomination. I think that credible threat is useful to get the Senate to perform its duty under the Constitution.
http://www.thesmokinggun.com/graphics/art3/0701051oconnor1.gif <- O'Connor Letter
