Every four years we hear that we have to put up a moderate Republican in order to win the national election, and every time we do that the Republicans lose.
It doesn't take a genius to see the pattern here. If you're going to lose the election anyway, why not put up a conservative candidate, someone that the conservative base can actually feel good about voting for? What's the worst that happens, you lose to a left-wing Extremist? And what's happened in the last two elections when Moderate Republicans were run? They lost to a left-wing Extremist (more specifically, especially this year, the moderate lost to a VULNERABLE Left-wing Extremist). If the worst that can happen is the status quo ante, why not change the game.