Most scholars believe, and aptly so, in my opinion, that it is almost impossible to pin down the fullest extent of the role which conservatism has played in American political history, or even just exactly what the term means in the first place.
Nonetheless, if taken in the literal sense, "conservatism" is simply to conserve something. Whether this be specific traditions, physical items, ideas, or the environment is inconsequential; essentially anyone can claim to be a conservative simply by virtue of being a collector. When brought into the political arena, conservatism, at least in its post-1980s incarnation, usually relates to the steadfast retainment of many economic principles held by classical liberalism, social views derived from often rigid interpretations of Judeo-Christian morality, and national security stances of hawkish origin. It is, in short, an eclectic mixture of laissez-faire and interventionist ideals, all sewn together through the notion of "peace through strength", as championed by former president and conservative standard-bearer Ronald Reagan.
As is obvious, conservatism has boundless positive contributions worthy of addition to several aspects of United States public policy. Particularly when it comes to fiscal and defense issues, its acknowledgment of a minimally regulated free enterprise system acting in harmony with strong, well funded military and police agencies equating in long term national prosperity is unrivaled by any other major school of thought. On social matters, however, it tends to turn away from reason and favor authoritarian approaches to handling the private affairs of private citizens.
This most unfortunate development is commonly manifested in actions and legislation crafted for the purpose of promoting "moral order" and whatnot, with those spearheading such movements believing that their opinions on any given subject are superior to those of others. Ironically, it is these people who find themselves in situations where their supposedly deeply held moral codes are not only broken, but in fantastical form. Relatively recent examples include now-retired Utah Senator Larry Craig and resigned Indiana Representative Mark Souder, both of whom were strong social conservatives, often stopping at virtually nothing to impose their beliefs on others, and each had his respective career foiled due to engagement in acts whose nature totally paralleled all that they preached. Craig, as luck would have it, was caught in a sting at a Minneapolis airport while practicing, shall we say, fancy footwork in a men's restroom stall. Not long after, Souder was essentially shamed into leaving Capitol Hill after it was revealed that he was engaged in an ongoing affair with a female staffer who was herself married.