The leader of the Senate Republicans (and albino sleestak) Mitch McConnell evidently hates tax cuts for the middle class:
Senate Republicans will oppose any effort to renew soon-to-expire Bush administration tax cuts if upper income taxpayers are excluded from the reductions.
A spokesman for Senate GOP Leader Mitch McConnell said Monday that every Senate Republican has pledged to oppose President Barack Obama's tax-cutting plan. [...]
McConnell has said a bill extending the tax cuts for only low- and middle-income earners cannot pass the Senate. Forty-one senators can block a bill with a filibuster, but McConnell spokesman Don Stewart declined to say whether all 41 Republicans would support a filibuster.
Smart move, Mitch. Now I hope the DSCC is producing a buttload of commercials about this. Ah, who am I kidding. A dozen Senate Democrats are probably going to filibuster with them.