It is a money thing. Sharron Angle, Christine O'Donnell, Carl Paladino, Ken Buck and Co. disprove this hypothesis swiftly.
Yet those are lower-profile races with less voter information. It is quite interesting that in the highest-profile primary race with a plethora of debates and constant coverage, the more moderate candidate is winning out.
If you want to use moderate in a relative sense but even then not really. Huntsman, Giuliani, McCain 2000, Bush in 1980...all losers. And if these Senate races were so low profile and low information, one would assume the candidates with the most name recognition would win. It isn't the case.
Point taken, though Huntsman never had a chance anyway & Giuliani forced himself into irrelevance (though he would have lost anyway). McCain 2000 failed due to a vicious smear campaign that was rather extraneous from his positions and I don't know too much about the 1980 campaign, except that the eventual nominee was extremely charismatic.
The Senate races weren't
that low-profile, but they were definitely lower in profile than the Presidential primaries. It seems to me that in the Senate races many people would probably notice who the Tea Party supported without hearing a lick of what that person had to say. Then again, maybe not. It's not like I'm in the head of the average Republican primary voter.