[slowernet]

Your question is probably rhetorical, but it happened because the Republican party decided they needed to bring social conservatives (especially Southern whites disaffected by the Civil Rights Act) into their coalition. See "Southern strategy" [1].

I believe anti-choice specifically was brought into the party platform during the Ford years. Outright homophobia was pretty mainstream until well into the 90s, and wasn't much of a differentiator between the parties. Democrats just soft-pedaled their position while the Republicans, specifically the fundamentalists who had grown in power since the 80s, made AIDS and gay marriage boogeyman issues in the "culture wars" [2].

For the record, both parties are coalitions and involve this kind of compromise between different constituencies (see Dems and organized labor, et al.)

[1] https://en.wikipedia.org/wiki/Southern_strategy [2] https://en.wikipedia.org/wiki/Culture_war#1990s

[FussyZeus]

Actually it wasn't, I appreciate the links. Thanks.