The reason the Republican Party has been incapable of developing and promoting an affirmative message is that the "evangelical" and "libertarian" wings of the party are wholly irreconcilable.
The Democrats had this problem. They had to pick between the "civil rights" wing and the "Dixie" wing. They opted, eventually, for civil rights, and lost the South that had voted Democratic for a century. In 1976 there were still a few left, but by 1980...
The Republicans need to decided if they are for small government or big government. If you are for small government, you can't be for a government that tells you who you can and can't have sex with, a government that wants to take control of women's bodies if there is a fertilized egg in them, a government which suspends the Fourth Amendment in the name of the War on Drugs, a government that wants to teach religion in science class, a government that wants to engage in foreign adventurism to build democracies abroad, a government that believes in torture, warrantless spying on US citizens, and massive giveaways to mismanaged businesses.
Look, white evangelicals aren't going to vote for a Democrat, because their ministers have spent the last 20 years telling them that they will go to hell if they vote for a Democrat. If the Republican party stops compromising its small-government principles on their behalf, they're still going to vote for Republicans. They won't work the phone banks and go door-to-door like they used to, but if the GOP can simply refrain from snickering at them like many Democrats do, white evangelicals will still pull the lever for Republicans even if the Republican Party gets out of the social engineering and moralizing business.
In return, the GOP might be able to harness the energy and enthusiasm of the Ron Paul supporters and the libertarians. Who, despite nominating Bob Barr, are generally opposed to everything the social conservatives are for.
The other problem is that for the GOP to be effective, it needs smart, capable leaders. It has, for the past twenty years, run on a sort of faux-populism that implies that smart, educated people are not real Americans, and that government is inherently evil. Is it any wonder that it keeps electing idiots who can't or won't use the power of government wisely? This trend has reached, if not its apotheosis, then at least a current high point in the way Sarah Palin was used in the general election. Sarah Palin may or may not be an dimwit; we can't know, because she was so carefully guarded. Her educational achievements were... limited, to say the least. She got her first passport two years ago. She seemed incapable of delivering a coherent response to a policy question. This doesn't necessarily make her an ignoramus, but it doesn't help. Then she went around the country arguing -- to cheering throngs -- that it you live in a large city, or in the northeast, or on the west coast, or had a graduate degree, or were black, then you weren't a "real American." Is it any wonder, then, that the GOP was crushed among educated voters? As David Brooks pointed out, the GOP's efforts to alienate educated, successful people have been so effective that even investment bankers donate to Democrats at almost twice the rate they contribute to Republicans. Not to mention doctors, lawyers, college professors, engineers, etc.
My advice for the GOP? Ditch the evangelicals. Dump the tactics of hatred, division, and fear. Take the position that social issues are like most other things: something the government should stay out of. Develop a series of cogent, defensible domestic and foreign policies which are consistent with a small-government philosophy. Don't demonize government; advocate for a small, but powerful and effective, government. Create a place for educated people and urbanites. Look, cities with virtual one-party Democratic rule since Roosevelt are being run into the ground by Democrats; people there are thirsty for change, but it can't come from the Republicans so long as the Republicans run on a platform of "we hate educated people" and a fair sprinkling of thinly veiled racism.
If the Republicans absolutely, positively must cling to a social issue, let it be abortion. Get rid of the gay-bashing, the abstinence-only, the creationism, the FCC-As-Your-Mommy, the Congress-Knows-Better-Than-Your-Spouse-When-To-Pull-The-Plug bullshit, the school prayer, the Ten Commandments, and the other nonsense and take a federalist stance on abortion, which is to say, our position on abortion is simply that the states should decide.