First of all, the definition of "conservative" with respect to policy matters has been shifting. Those who hold to the version of conservatism espoused by the 1950s National Review such as Alan Keyes are considered far right zealots. Those who adhere to Jeffersonian, limited, Constitutional government principles, such as on Paul, are viewed as obstructionists or just plain weird.
The dominant wing today is neo-conservatism, which on foreign and most domestic matters differs little from the principles of Franklin Roosevelt or Lyndon Johnson. (They are somewhat more pro-free market and more skeptical of Maxrism, however.) The "compassionate conservatism" of the Bush administration is merely the Great Society with a few "Amens" and "Hallelujahs" thrown in to please the Christian Right. The bottom line is: Goldwater and Taft would have recognized Keyes and Paul as allies and co-thinkers, while regarding William Kristol and Bill Bennett as being on the other side.
Secondly, every passing year sees an increase in the Hispanic population via high birthrate and immigration, legal or not. With the singular exception of the Cuban-Americans, the Hispanic population has leaned leftward. Historically, most immigrant populations since the early 1800s have been inclined to the political left, with the most notable exception being British and Dutch Protestants, and, to some extent and in certain areas, Irish and German Catholics and Lutherans. However, with the singular exception of the Eastern European Jews, upward mobility and assimilation tended to move the descendants of the immigrants to the political center or right.
The differences with the Hispanics are that they are united in language. Eastern European immigrants - Poles, Czechs, Croatians, Hungarians, and Lithuanians - came from a common geographic region and shared, for the most part, a common religion and had some cultural similarities. However, their languages were mututally unintelligible and national rivalries were strong. Hispanics of different nations share a common language and do not suffer the degree of national rialry that Eastern Europeans have. Hispanic leaders, unlike Archbishop John Hughes and Carl Schurz, leaders in the Irish and German communities, respectively, in the mid-1800s, do not promote assimilation, but rather fight it. With bilingual education, Hispanic TV and cable networks, radio, and print media, it is far easier for a Mexican to live an All-Spanish life in Los Angeles circa 2003 than it was for a Pole to live an All-Polish life in Gary, Indiana circa 1913.
The bottom line is that the Hispanic vote is growing rapidly and is owned by the Democrats.
Yet another factor is leftward political drift among native-born whites, especially in the upper and upper middle classes. The pattern of conservative parents and liberal offspring is a common one. Think of such names as the Tafts, Kennedys, Fords, Rockefellers, Pews, Buffetts. You even see the pattern of a liberal widow of a conservative husband, such as the wife of the late Ray Kroc of McDonald's fame. Is this just a problem of the very wealthy? Hardly. Look at the voting patterns of middle and upper middle class British descended Protestants in New England and the urban Northeast, the epitome of the WASP. In the 1920s and 1930s, they were known as rock-ribbed Republicans and their political archetype was Calvin Coolidge. Their grandchildren are almost as consistently liberal as they were conservative, albeit with some residual GOP loyalty, the so-called "country club Republicans." Their voting patterns are similar to those of the grandchildren of Eastern European Jewish immigrants, whose grandfathers were heavily immersed in one or another socialist philosophies.
Heroic efforts by private and home schoolers, evnagelical churches and parachurch ministries, and evangelical (and more recently, right-wing Catholic) colleges and seminaries may be insufficient to stem the overwhelming tide of secular humanism and liberalism, deeply entrenched in the public education system, from pre-K to graduate school, and in the mainstream media. One survey cited by Campus Crusade for Christ claims that one-half of those students who describe themselves as born-again Christians no longer use that term by senior year. Surveys also indicate that over 80% of evangelical Christians send their children to public schools. An unacceptably high number of them watch the same trashy movies and TV and listen to the same rotten music as their non-evanglical peers.
In other words, it is not inconceivable that the grandchildren of the Christian Right of the Bush 43 era may become as leftist as have the grandchildren of the rock-ribbed Republicans of the New Deal era.
I really hate to be a pessimist, but I fear that in 10-15 years we will count ourselves lucky if we can get a liberal Republican like Rudy Guiliani or Colin Powell in the White House, or even a less radical Democrat like Joe Lieberman. The train riding away from our nation's Christian and Western heritage and its legacy of limited government and inalienable rights has been on track for well over a century and I don't see, humanly speaking, anything strong enough to resist that train going all the way to serfdom for the masses under a self-perpetuating oligarchy.