My suspicion is that he figured there was a strong chance that Romney would lose (I expect his aides were telling him what was going on in Virginia) and that he needed something to help oust Boner in whatever Congress would emerge from the election. I think it's quite possible that the tea party element will try to remove Boner if they perceive him as giving away too much in the lame duck session.
"A mediocre person tells. A good person explains. A superior person demonstrates. A great person inspires others to see for themselves." -Harvey Mackay