The fact is this:
Democrats know that the way to win in conservative districts is not to run a liberal. There are still conservative Democrats out there, after all.
Republicans, being purists, insist on running only the most conservative candidates, which will never get them elected in liberal areas. There are no liberal Republicans any more.
So what happened in this election? The people, when given a choice between two conservative candidates, chose the Democrat. Why? Because poll after poll shows that while they distrust both parties, they distrust Republicans even more.
Backpedaling and pretending that the GOP never claimed they would win this and then trying to explain it away by saying "he's a conservative" cannot negate the fact that a Democrat won.
The predictions of a great Republican takeover just haven't happened. (In fact, of the last 4 special elections, Democrats have won all of them.)