A wide variety of people who call themselves conservatives have many different definitions of what a conservative is. But for me the starting point is personal freedom and the God-given right to be free from the restrictions of arbitrary force that is the bedrock foundation of the U.S. Constitution and the rule of law.
Because political freedom and economic freedom must go together, in addition we believe in that a market economy that allocates resources by the free play of supply and demand is the most productive engine of human needs and it is at the same time the best economic system that is compatible with our personal freedom. Beyond these essentials all other issues are transitory.
From the time of President Harry Truman to the time of President George H.W. Bush, the Cold War between the Soviet Empire and the Western alliance dominated foreign policy decisions. Since about 1993 with the first attack on the World Trade Center, international terrorism and homeland security have dominated both foreign and domestic affairs.
Illegal immigration was an issue even before Reagan's 1980 election but not nearly as intense as it became in recent years. President Bill Clinton in 1992 ran on the slogan, "Its the economy stupid." and of course that still is a dominant issue but it could be turned around now against the party of Bill Clinton.
Honest differences over trade policy, education, pro-life, tax policy, and health policy have been with us since 1973 but the exact mix of issues keeps changing so all issues are temporary. Principles only are permanent. What is most important is the compass we use to discover if we are going in the right direction or not. In my opinion if we are advancing in the direction of more personal freedom then we are going in the right direction but if away from personal freedom we are going in the wrong direction.