Who and where are they? If there are any, they are few and far between. That's who lost in 2006 and 2008, RINOs in seats that couldn't be gerrymandered against rats that claimed to be prolife, pro 2nd amendment, fiscally conservative, etc., as needed where needed. According to Michael Barone in a recent column, 43 % of GOP House members were elected in 2010 and 2012, i.e. the Tea Party cohort.
I will say that for the most part, the only vulnerable republicans in the house are “rinos”.
That is because the hard line conservatives are in safe districts while the rinos are usually in the swing districts.
Lets face it. Who was more vulnerable last election, Ted Cruz from Texas or Scott Brown from Mass.
Basically, the conservative is never elected in a swing or dem leaning district so they are never an incumbent who can lose. While the moderate is usually never in a safe seat.