Null and void by whose standards? If the Dems break their promise (which they will, they always do) they know they'll have the same RINO's to give them cover and make yet another "deal".
It's the power of seven RINO's in a 55 person R delegation. It's been like this for years. Even the "great" *cough* Trent Lott couldn't handle it.
BTW, the seven or more RINO's could do the same damage in the up-or-down vote.