This is probably fine... The Senate almost invariably turns erstwhile Conservatives into liberal pod people. Since they don’t have to run until every six years, they tend to get fat and more susceptible to corruption than those on a shorter leash (those that have to run every two years). I hope Ted Cruz proves to be an exception, but he will certainly have to withstand a bunch of crap from the Media and pod people Republicans (e.g., McCain, Lindsey, etc).
He won’t have to withstand Linseed Graham much longer, God willing.
Part of it might be the six year term lets them do whatever they want without facing repercussions from voters, and there are certainly examples of people in the Senate (as well as the House) who get Potomac fever and "evolve" after many years in office (Tom Coburn, etc.) However, I think a big part of the problem is a lot of these "tea party" Senate candidates just weren't very conservative in the first place and the tea party simply backed the wrong horse in the primary. We can't afford anymore Rob Portmans.