I think what the GOP is really missing is a particular kind of realist - a Hamiltonian. The pre-war GOP had two wings: Jeffersonian (isolationist) and Hamiltonian (internationalist). The "liberal internationalism" that dominated the Democratic Party and the nation from FDR to JFK was a marriage of Hamiltonianism and Wilsonianism; in this period, the GOP's Jeffersonian wing was entirely discredited, and what grew in its stead was a Jacksonian wing. The Vietnam War led to the emergence of a left-wing Jeffersonian wing in the Democratic Party, while the neo-conservatives brought Wilsonianism into the GOP so that, by the time of the Reagan Administration, the big tent enclosed Hamiltonians, Jacksonians and Wilsonians, while the Democratic Party was divided between Wilsonians and Jeffersonians.And so they have, it seems. Now the question is whether the GOP can endure as a Wilsonian-Jacksonian coalition, or whether it needs a strong infusion from another quadrant to be viable politically and (especially) capable of effective governance.
The Bush Administration's foreign policy has been a blend of Jacksonian and Wilsonian impulses. Post-Fiasco, the divisions between these views - between the "to hell with 'em hawks" and the neo-conservative true believers - have been sharpened, but between them you still encompass the predominant strains of thought within the GOP (albeit Ron Paul has embarked on a one-man crusade to revive the pre-WWII Jeffersonian wing). But this is precious little sign of a revival of Hamiltonianism - a hard-headed realism that is internationalist in orientation.
At least, there is precious little sign within the GOP. Daniel Larison has mocked Senator Chuck Hagel for calling his colleagues "insulationist" - what he means to call them is "Jacksonian." They aren't "isolationists" (Jeffersonians) but they are introverted - they don't care about the rest of the world, don't see our interests as inextricably entangled with other powers in the international system. They just want to pound the bad guys into rubble like we did in good old dubya dubya aye aye. Hagel is a Hamiltonian; so is Lugar. And, as you might have noticed, they are being run off the reservation even though, as Larison notes, they have not actually repudiated interventionism at all (which, as internationalists, of course they cannot).
The more interesting question is whether Hamiltonianism will be revived within the Democratic Party. As a (mostly) Hamiltonian myself, I certainly hope it is revived somewhere, for the sake of, well, the national interest. But I would also argue that a strong Hamiltonian wing is what the Democrats need to win the Presidency in a post-9-11, post-Iraq America where national security really does matter to electoral success. To date, the Democrats have tried to demonstrate their national security seriousness through two strategies: putting up Jeffersonians in uniform and putting on unconvincing displays of Jacksonian rhetoric. Both are insufficient - the latter is even counter-productive when done clumsily, as it usually is. The hurdle they have to clear is not really related to patriotism or willingness to serve; it's mostly related to seriousness about the national interest. America's confidence in the Democratic Party as steward of the economy and of the national interest was dented by Lyndon Johnson and then shattered by Jimmy Carter. Bill Clinton restored American confidence in the former, but did nothing to restore confidence in the latter. The Bush Presidency gives the Democrats an opportunity to present an alternative foreign policy vision and regain confidence in that area as well. If that alternative vision is articulated in Jeffersonian terms, whether by a Yankee patrician or a Southern good ol' boy, I don't believe it will win that confidence. They might still win, of course, as confidence in the GOP has been badly damaged. But if they want to change the game, they should be looking for Alexander Hamilton.
One way to think about this is to imagine a variant on the Millman Chart that organizes the four tendencies by their relative hawkishness: In this division, the Wilsonians and Jacksonians would both fall on the hawkish side of the line, while the Hamiltonians and Jeffersonians would be - well, "dovish" is probably the wrong word for Hamiltonians like Dwight Eisenhower, George H.W. Bush and (to a certain extent) Ronald Reagan, but at the very least it's safe to describe the Hamiltonian tendency as much more skeptical about the utility of military force than either the Wilsonians or the Jacksonians. At the moment, then, the Hamiltonian shift toward the Democrats leaves the GOP dominated by two factions that both tend to err on the side of hawkishness in any given foreign-policy controversy - and this strikes me as a profoundly unhealthy development.
In theory, one could imagine this problem being solved by a revival of Ron Paul-style right-wing Jeffersonianism (which aspires, of course, to drive the Wilsonian neocons out of the party, and create a Jacksonian-Jeffersonian GOP). But despite Paul's fundraising numbers and Daniel Larison's prolific blogging, I don't think there's enough life in Right-Jeffersonianism to make it a plausible force in our national politics. (Nor do I think that a Jeffersonian-Jacksonian "coalition of the introverts" could govern the nation responsibly unless the United States actually withdrew from its current quasi-imperial role, which almost certainly isn't going to happen.) There is, however, plenty of life in the Hamiltonian tendency - despite the fact that many of its practitioners, starting with the buffoonish Chuck Hagel, did not exactly distinguish themselves during the debates over the Iraq War - and the exodus of the Scowcroftians to Obamaland notwithstanding, I still think that the congruence between the Jacksonian views of the GOP base and a Hamiltonian take on the world offers fertile ground for a right-realist revival. It probably won't come from the Hagels and Scowcrofts and their peers, but I'm optimistic that you'll see it in the next right-of-center generation - the twentysomething and thirtysomething conservatives for whom the Iraq War was a formative (and chastening) experience.