Scott Walker has concerned many Democrats for this very reason; he has managed to win several elections in a blue-tinted state even while being quite right-wing. Fortunately, there is now good evidence that Walker isn't exactly prime-time ready. Liberals were driven crazy by the media's refusal to acknowledge Paul Ryan as a creature of the far-right (and for acting as if he's handsome, when he is very clearly a White Walker). But I haven't heard a lot of buzz around Ryan this time around; maybe his moment has passed.
The current darling of the far-right is Texas Senator Ted Cruz. On the metric of "how would he do as President", he's an easy case -- the guy is a lunatic who would make for a catastrophe if placed in charge of the country. The question is whether there is anything that would make him more electable than his extremist profile would suggest. And after much thought, I've decided the answer is no.
Let's dispense with one obvious possibility: Cruz's Latino heritage. I don't think this will meaningfully help him amongst Latinos. Despite what the media might think, Latinos, like Black people, are not retarded kittens -- they vote, the same as most of us, on the basis of a judgment regarding how a given candidate matches up with their political and policy priorities. Cruz's policies (especially on immigration) don't line up with most Latinos, and they know it.
As for everyone else, here is my proposition regarding Ted Cruz, on which I welcome your input:
Ted Cruz : Presidential nomination :: Robert Bork : Supreme Court nomination.Ted Cruz (like Robert Bork) is a very smart man. But he is also a supremely arrogant man. This distinguishes him from, say, Sarah Palin, who is supremely arrogant but also dumb as a post. But Cruz, like Bork, thinks so highly of himself that he can't even pretend to present himself as mainstream. Bork was successfully Borked mostly because he was allowed to hang himself -- Bork was so confident that his constitutional vision was correct that he presented it completely unadulterated, and Democratic Senators were happy to let him wax lyrical. The result was a nominee who was terrifying to the general public. I have no doubt Cruz will do the exact same thing. He is, I think, incapable of pivoting to the center even as a matter of image. His inflexibility on this is part of the reason why many in his own caucus hate him -- Cruz loves to get up on his grandstand and is happy to do so even when it hurts his own party. So far, it has helped him just fine, since he's in a solid red Senate seat. But when trying to appeal to voters in Virginia or Minnesota or Nevada? Yeah, best of luck.
Ted Cruz is a smart man who would make a terrible President. Fortunately, he'll make a terrible presidential candidate too.