Did the "Tea Party" lose the Senate for the GOP?
Any argument that they did is at least somewhat misleading and self-serving for Dems and the Tea Partiers' Republican establishment opponents. Because you can't just look at the marquee Tea Partiers that went down. That's not the whole picture. You also have to take into account how Republicans won in Illinois and Pennsylvania and put up smashing wins in New Hampshire, Indiana and Ohio. Those wins were won on the basis of "Tea Party" intensity.
Having said that, when Tea Partiers won Senate primaries the results were terrible. There's little question Republicans would have won Delaware if O'Donnell hadn't been the nominee. Reid would have been much harder pressed to win if not for Angle -- though his margin ended up being pretty good. Miller was a disaster in Alaska. Murkowski ended up saving the GOP's bacon. Miller's popularity collapsed so dramatically and McAdams (D) was so personally popular that I think he likely would have won if Murkowski hadn't decided to run as a write-in. Colorado I'm less sure about since Buck -- though given the Tea Party label and the guy who knocked off the establishment choice -- simply wasn't in the same league of cartoonishness as the other three. But you can make at least a plausible argument that each of those seats would have been gettable with better candidates.