Nixon didn't stop Wallace at all, Wallace got 5 states in 1968 but got shot in 1972 in the middle of campaigning and dropped out. The Dixiecrats were already leaving the Democratic party because of its late 1960's liberalism--read some of their
actual statements on why they switched. Blacks had been switching their votes to Democrats since FDR, because the New Deal benefited them economically. And the Democrats picked up the more conservative south whenever they ran a Southerner like Jimmy Carter or Bill Clinton.
Reagan didn't spawn a new coalition of crazy religious people and wingnuts. Reagan had been a Buckley/National Review brand New Right conservative since the late 1950s, before the Civil Rights Act was ever written. He gave his
Big Tent speech in 1967, when Nixon was still a failed candidate and was nowhere near the 1968 nomination. Relevant paragraphs for those who never read it:
The Republican Party, both in this state and nationally, is a broad party.There is room in our tent for many views; indeed, the divergence of views is one of our strengths.Let no one, however, interpret this to mean compromise of basic philosophy or that we will be all things to all people for political expediency.
In our tent will be found those who believe that government was created by We, the People; that government exists for the convenience of the people and we can give to government no power we do not possess as individuals; that the citizen does not earn to support the government, but supports a government so that he may be free to earn; that, because there can be no freedom without law and order, every act of government must be approved if it makes freedom more secure and disapproved if it offers security instead of freedom.
Within our tent, there will be many arguments and divisions over approach and method and even those we choose to implement our philosophy.Seldom, if ever, will we raise a cheer signifying unanimous approval of the decisions reached.But if our philosophy is to prevail, we must at least pledge unified support of the ultimate decision.Unity does not require unanimity of thought.
Yes, the Religious Right were in that tent during the 1980s, but not exclusively so. Joe Lieberman and Tipper Gore, who led the moral crusades against video games and music respectively, were Democrats.
Bush Sr inherited the Reagan coalition, but it wasn't until Bush II that anyone devoutly Christian could only find a home in the Republican party. By that point, the reasons were completely disconnected from Johnson, Nixon, racism, etc.