Because conservatives tend to turn a LOT of folks off...
For instance, I don't care what someone does about birth control, I don't care what they do in the privacy of their own bedroom as long as it doesn't hurt children or animals, I'm not for the death penalty (but I am for Really Really Hellish Desert Prisons), I'm not concerned about the damage to the desert habitat, I think they should legalize any recreational substance anyone wants, as long as they do no harm to other people (in which case there's that desert thing...), etc., etc... I think that some social financial programs do have a place, but I think those places oughta get looked at occasionally, and if the pantry's full of junk food and there's a big screen, bye-bye check... Do it twice, well, there's a chance to get real friendly with Mr. Gila Monster, who is real pissed about that habitat thing...
Pretty much the ONLY thing holding me toward the "conservative" side is gun control.
I don't want to go to a gun show, and have some genius telling me at the door that the only way I can be "saved" (using several syllables to do so...) is via his own particular brand of twaddle, and no other. I shoot snakes - I don't dance around with 'em.
There are LOTS of right-leaning folks... Problem is, we lean to far, and we get completely disgusted.
If the Republicans up and said "Hey, we're gonna leave this abortion thing alone - people can work it out in their own consciences" and "who you wanna have for a life partner is between you and them, not you and the state," they'd likely gain a good 20-25% right there. And the anti-abortion activists, etc., would go vote for someone with the same chances as Ron Paul, who would have about the same numbers.