While some of my political views are even what could be described as conservative, I've found the modern Democratic Party far more accomodating of my centrist beliefs than the Republican Party.  If the pendelum swings enough to the left that the liberal wing of the Democratic Party gains enough political control that it feels it doesn't need to accomodate centrists like me, I wouldn't hesitate to switch parties.  At this point in history, the Democratic Party is where the political center is at.

The major political parties in the United States are not religions with fixed dogmas.  They are coalitions of people with often different interests.  When a majority of members of a political party attempt to establish "core values" as with a religion it erodes the coalition and loses elections.