For those that say he cannot be teabagged, think again. The GOP has proven they're not smart (stated above) and they threw some easily winnable seats away in Nov. Worse, you listen to some of those idiots talk and you realize how uneducated some Americans are.
I agree that it is possible he will be primaried, but doesn't most Republicans and Republicans in MA understand that Scott Brown is the best thing that has happened for them in a long long time?
Why throw that away just because Jim DeMint, Sarah Palin and the retards at RedState.com says he isn't pure enough?
The non-political answer to your question is that people are morons in this country. Hell, most Americans can't name their House Rep, Governor or Senators. Education has gone to hell in this country. Thus, you listen to what other morons around tell you, including people like DeMint who continues to prove to be one of the most intolerant freaks; of course in this great land, he's gaining power within the party.
20 years from now, people will still remember that DE Senate race and ask the GOP voters there, what the hell were they thinking?