The problem is the far right of the country has become so demanding that any straying away from a hard conservative image is frowned upon and shunned. So to keep them happy and the independents you need to get elected happy at the same time...the candidate has to perform an awful dance of "I'm super conservative and on your side" and then "I'm moderate and on your side" and it's been shown over and over that just doesn't work.
The reason it doesn't work is because dancing around between conservative and moderate demonstrates a complete lack of understanding regarding conservative principles. True conservatives know this, so as soon as this "dance" begins, they tune out and turn off. Mitt Romney's biggest problem was, he didn't believe he could win. He lacked the conviction of a true conservative who believed in a conservative message. Contrast this with Ronald Reagan, a man who knew what Conservatism was all about and was comfortable taking the time to explain it, argue for it, stand up for it. We need someone with that kind of confidence again, who isn't afraid to be a conservative.
I will add this as well, social values play a vital role in Conservatism. It's part of the package. To try and weasel around this and pretend to be a "fiscal conservative" while embracing "social liberalism" is anathema to conservative principle. It demonstrates that you don't really understand Conservatism. Does that mean you have to go out there and sound like an evangelist? No, Reagan certainly didn't, but he maintained a strong belief in social conservative philosophy and defended it to the hilt. He didn't back away or shy away from social conservative values, he embraced them and explained why they were important.