I think it could be fruitful to examine the conservative/liberal clash in the USA as being analogous to, and in fact in some sense reprising, the clash between Romanticism and Enlightenment.
Warning: long.
Historical and philosophic background.
First, a quick introduction. Romanticism and enlightenment are two of the dominant intellectual paradigms which have shaped our culture. Enlightenment was, in a sense, the outgrowth of Renaissance, the ultimate rejection of the perceived darkness and barbarism and anti-intellectualism of the medieval Europe. Enlightenment was the Age of Reason, when men thought that the whole world was theirs for the taking, to learn and understand and control. Enlightenment thinkers were radically anti-clerical, and often anti-religious. Deism (the belief that god created the 'clockwork Universe' and walked away, responding to no prayer and intervening in no human affairs) was a very popular metaphysical view. US Founding Fathers were the children of Enlightenment (which I will henceforth abbreviate as 'CotE'), and many of them were deists.
Romanticism arose in late 18th and in 19th century. It started as a backlash against Enlightenment -- specifically, against the enlightenment rationalism. Romantics thought that the Enlightenment philosophes had reduced humanity to clockwork, excising all freedom and passion from life -- unweaving the rainbow, so to speak. Romanticism was often reactionary, harking back to the idealized earlier times, though not always. Many Romantics were instead radical progressives. What united them was not a cogent political programme nor a singular metaphysical view, but rather the opposition to the perceived excessive rationality of the Enlightenment; it was the idealistic, almost anti-rational exaltation of man as a passionate and aesthetic, rather than rational, being. Fundamentally, Romantics were opposed to empirical reason, and sometimes, though not always, anti-intellectual in general.
Of course, Romantics were critically wrong in one key regard, and this one point is of critical importance. Understanding optics does not unweave the beauty of the rainbow, and rational understanding of the world and man does not strip life of joy and beauty. However, Romanticism being a deeply a-rational (though not necessarilyanti-rational) perspective, that reasonable position simply holds no sway in the face of passionate rebelliion against the perceived Enlightement strictures. Nevertheless, that rebellion is deeply, profoundly misguided, based on the idea of mutual exclusivity which is false, the corrosive idea that, fundamentally, familiarity breeds contempt, that spirituality can only thrivce in mystery and thus ignorance -- the destructive that reductive knowledge and normative value are mutually exclusive.
Modern times.
Liberalism is the intellectual descendant of Enlightenment (among other things). We think. We reason. Our communications tend to be conceptual (we communicate ideas). We try to communicate in terms of concepts, ideas, issues and realistic solutions, even as our fundamental ideals guide the direction of the inquiry (here we again see how within the Enlightenment framework, empirical knowledge and normative values coexist in synergy). Our candidates run on platforms of issues. We really believe that we can execute the political process through rational exchange of ideas. We keep saying things like 'yes, this is what we want, but what is the best way to achieve it?' (e.g. yes, we all wanted Saddam out and Iraq democratic, but is a war really the way to do that?)
Modern conservatism is a child of romanticism (notice that I say 'modern', I lay no claim to my analysis holding beyond the last couple of decades). Just like the original romantics, conservatives can be both knuckle-draging reactionaries and passionate neocon idealists, though ironically, neocons are themselves intellectual children of Leon Trotsky, who was also a romantic. Conservatives' communication is largely phatic, as our own DHinMI noted -- not for the purpose of conveying information, but for the purpose of establishing social relations and forming group bonds. Their candidates run on image (or 'character', as they like to call it) -- itself a romantic idea that a man's character, his soul, is the best way to understand a man and to contextualize his interactions with the world.
Note that none of this implies that intellectualism is antithetical to modern conservatism. However, the conservative intellectual brigade tends to approach matters along the line of a-priori reasoning, reasoning from abstract principles which may or may not have anything to do with empirical reality. We see this most starkly in the Libertarian camp; however, we also see this a-priori reasoning in conservative approach to foreign policy, environmental policy, welfare, etc. They reason from how the world ought to be, rather than from how it is -- in radical contradiction with what the term 'conservative' had been generally used to mean.
A friend of mine, when I showed him an earlier version of this article, came back with the Apollo/Dionisius/Cygnus comparison, CotE being with Apollo, and Romantics being with Dionisius, with neither approach being sufficient by itself; but I see Enlightenment as Cygnus, the framework which allows reason and passion to coexist, contrary to the Romantics' rejection of Enlightenment's enabling of such synergy.
By the way, this idea also finally answers my persistent puzzlement as to why Libertarians, who should seemingly be aligned with old conservatives economically but with liberals socially, end up being politically aligned with GOP as a whole -- they too are Romantics, and what matters more is not ideological alignment, but the aforementioned meta-cultural similarity, the deeper allegiance to Romantic mode of thought and interpretation.
More broadly, we can see the Romantic trends in today's conservatism. Though they claim a conservative ideology, there is actually no cogent ideology behind it -- the 'small government' schtick is gone and was in fact never really there, and the 'individual liberty' thing was always a sham. Conservatives decry Bush's departure from the conservative ideals -- but you think back about the reality of GOP (rather than their proclamations), there aren't any such unifying philosophical views, not even in a very broad sense. What unites today's conservatives is not specific beliefs, but the method -- the way they look at the world, rather than that what they find. To put it as briefly as I can, modern conservatism is defined not by ideology but by a meta-cultural perspective -- Romanticism; which also explains why the reasonable and moderate 'conservatives' are unwelcome in GOP.
Examples.
These differences keep hitting home in drops and dribbles. Just the other day, I was speaking to a conservative about welfare. She was objecting to welfare being abused, so I mentioned to her that at a certain point, the society's cost of poverty (in crime, lost skilled labor, mental and familial problems, etc.) is greater than the society's cost of alleviating poverty -- which is basically Milton Friedman's argument for a minimalistic welfare state administered through Negative Income Tax (Milton Friedman being the uber-conservative economic luminary and Nobel laureate). This idea was totally alien to her -- she was simply having trouble slipping into 'this is the problem, what is the best way to solve it?' mode of thought. All she could do was think in terms of idealized value arithmetic -- i.e. that welfare abuse is bad, and welfare encourages indolence.
I saw another example of the same thinking recently, too -- in an uber-conservative Russian emigrant I had spoken to. He just couldn't get past the 'the lazy parasites don't deserve my money' barrier. Any discussion of economic efficiency or optimal resource allocation would always come back to saying that welfare supports unemployed troglodytes. Actual empirical facts and rational arguments based thereupon, held no sway.
Then of course there's the earlier-referenced entry by DHinMI, showcasing the example of phatic/conceptual communication gulf between congressional Democrats and Republicans, exemplifying the larger cultural gulf between CotE and Romantics.
Analytical applications.
Overall, I think that the american liberal/conservative distinction can be gainfully analyzed though the enlightenment/romanticism comparison, and that perhaps we can even see today's struggle between liberalism and conservatism as reprising the original Enlightenment/Romanticism clash, where Romanticism was a backlash against perceived (but not in fact existent!) dehumanizing hature of Enlightenment.
A few simple conslusions I have come up with, by examining the situation through this filter:
For one, I think the real internal gulf within the modern conservatism is between endangered empiricists, and the romantic anti-empiricists; between the 'reality-based community', and the rest. Neocons, theocrats, hard-line libertarians, and many paleocons fall under the romantic rubric; yet many paleocons, moderates, and libertarians are also CotE, and would lean towards empiricism rather than romanticism. This in turn would indicate that attacking the faultline between, say, neocons and theocrats, it relatively pointless, as that faultline is non-essential to conservatism as it's currently structured -- those groups tacitly accept their difference because they recognize their similarity as romantics, respecting and setting aside each other's differing principles in favor of their common desire to place their particular abstractions above hard reality.
Another conclusion would be that attacking modern conservatism ideologically should be done not by attacking it for being wrong (because wrongness of any specific position has absolutely no relationship to modern conservatism's status as a whole), but by attacking it for being inconsistent -- really drive home the fact that conservatism has no ideological coherence, since that (in my experience) is the illusion many harbor, that conservatism is an ideology in a broad sense. On a conscious level, people speak about conservative ideology without bothering to explicate the inexplicable -- the non-existent ideological principles comprising conservatism -- and it is this lack of ideological coherence that they may be forced to confront, whereas now, because they think the ideological coherence is there, the 'conservative ideology' becomes to each person whatever it is that allows them to feel as if they belong with conservatism ideologically. This BTW explains how so many conservatives so wildly misinterpret Bush administration's issue positions -- conservatives tend to simply assume that conservatism is an ideology, and that therefore other conservatives must share one's ideological views.
Perhaps realizing that modern "conservative movement" makes only marginally more sense than something as frivolously arbitrary as a hypothetical "chocolate-lovers' party" ideologically, will have an effect of focusing the public discourse on the matter.
Conclusion.
I often see people speak about the modern conservatism's inconsistency and its divergence from what 'conservatism' actually means as a term, but understanding why it nevertheless remains a cohesive political force, and even a sociopolitical movement and identity, is the $64K question.
P.S. Nationalism is generally romantic. Fascism almost always is. Communism, in its subjugation of reason to ideal (e.g. Lysenkoism) also came down on the romantic side of the equation.