It's pretty much a given that the Tea Party cost Republicans the Senate seats in Nevada and Colorado this week. We have some data from our final polls in those states that sheds further light on that.
Our final Nevada poll found Harry Reid behind 47-46. It also found that in a hypothetical match up with Danny Tarkanian Reid would have trailed 54-39. Obviously we underestimated Reid's standing against Sharron Angle but given that he polled 14 points worse against Tarkanian it seems pretty safe to say that even with his 5-6 point victory Tuesday he would have lost by a similar margin had Tarkanian been the nominee instead.
The big difference between how Angle and Tarkanian would have fared against Reid is with independents. We found Angle leading Reid by 14 points with them...but we found Tarkanian up by a whooping 40 point margin, 66-26. There were a lot of independent voters in Nevada who were inclined to vote against Reid but just thought Angle was a step too far.
In Colorado the difference is not quite as stark but it still seems likely that nominating Jane Norton instead of Ken Buck would have given Republicans a 1 or 2 point victory in the state instead of a 1 point loss. Our final poll found Buck leading Michael Bennet by a single point. It also found that Norton would lead Bennet by 4 points in a hypothetical contest. Norton performing 3 points better than Buck against Bennet is consistent with our polling over the course of the entire cycle- across all of our pre-primary Colorado polls Norton did on average 2 points better than Buck. Given the razor thin margin of Bennet's victory the outcome may well have been flipped with Norton as the nominee.
The reason Norton would have done better is the same reason Tarkanian would have- better appeal to independents. Bennet's approval numbers with independents were pretty miserable- and we found Buck with a 4 point lead among them. But we found Norton up 11 points on Bennet with them.
Obviously you can never say exactly how things would have unfolded had Tarkanian and Norton been the nominees. Maybe months of attacks on them would have led to the same final results. I doubt it though. Reid and Bennet are not popular Senators. They would have been defeated by mainstream Republicans...but GOP primary voters overplayed their hands.