The Republican Party has indeed deviated from conservatism as it is understood by those who consider Edmund Burke the founder of the conservative idea, William F. Buckley the intellectual midwife of modern-day American conservatism, and Barry Goldwater the flint that sparked a vast political movement in favor of small government in the United States.
This deviation expresses itself in different ways. First, in the confusion between Jeffersonian populism—a salutary mistrust of economic power allied to political power—and class-based populism, which is what Republican leaders promote when they scorn America’s coastal and big-city culture. Second, in the contradiction between a low-tax, low-spend policy and an interventionist foreign policy that, by definition, is costly—as every empire in the history of mankind eventually and painfully found out. Last, in modern-day Puritanism, which started, perhaps understandably, as a reaction against the cultural excesses of the 1960s but ended up turning into what H.L. Mencken described decades earlier as “grounded upon the inferior man’s hatred of the man who is having a better time.”
I'll admit that the philosophy of Edmund Burke is "above my pay grade", as they say. Of the three pillars of modern conservatism, the populist mis-trust of economic/political power and adherence to traditional modes of conduct, seem to be pretty well rooted in the Republican party. It's the small government versus strong defense problem that is the biggest obstacle to a coherent modern conservatism. Eisenhower's nightmare scenario of the "military/industrial complex" has not only come to pass, it has left the country behind.
A stout defense is essential in the modern world, but since the end of the cold war we have found ourselves with few adversaries to defend against. The current war against the Jihadi movement has proven to be an expensive undertaking with little to show for it. Killing a few terrorists with a multi-million dollar satellite guided smart bomb is just not cost effective. Meanwhile, NATO expansion and military commitments defending wealthy client states proceeds unabated.
What is needed to complete a Republican inter-party revolt is the recognition of the limits of military power. Either the hawks will need to find a new home, or the libertarian right will. With the neo-cons seemingly in full retreat, there is an opening here for the limited government/limited military option to recreate the third pillar.