The heart of conservatism, as elucidated by its progenitor, Edmund Burke, is a healthy respect for the messy, inconsistency-laden reality of human institutions as they have actually evolved across generations. Such institutions are necessarily imperfect, but have value by the simple virtue of having withstood pressure over time. You discard such institutions only with great caution; what is destroyed overnight can take decades to rebuild. This is where we get the very term "conservative"; conservatives believe in the conservation of human institutions and values. Conversely, the word "radical" derives from the Latin for "roots," because radicalism is all about digging things up at the roots and starting over.
Both impulses have their place in society. But our national politics have reached the strange tipping point at which the two labels have become reversed: they now hang from the necks of our politicians and parties like mixed-up nametags.
The Republican, "red state" agenda can be called "conservative" only by force of habit. Abroad, President Bush pursues a messianic vision, one part religious war and one part democratic crusade, neither pursued with any consistency but both leading to regime changes, bloodshed and the casual abandonment of carefully built institutions and alliances. At home, Bush, having enacted massive changes to the federal tax structure that are steadily bankrupting the government, seeks to scuttle Social Security, the most successful social program in American history.
The president is a radical. It is his Democratic opponents, fighting a rearguard action to protect the institutions of the liberal state that their predecessors built over the last century, who are now conservatives.