An interesting hypothesis. I wonder if the gay movement would really cause a schism over this. The (American) gays have to know that without Democratic support, they are dead in the water. Besides, whether there is a gay gene or not (I think the Bible holds 'no'), we all know that many gays do actively recruit the troubled and lost. Fresh meat. Further, and I don't know how prevalent this is, but I thought that gay couples were getting together more and more to exchange DNA and then split up the litter of human babies between the male and female couples. No risk of abortion there. Overall, my guess is that the homosexual lobby simply needs the DEMS too much.
Since gays are only 3% of the population any abortions to avoid a gay child will have impact that they themselves could not overcome through any combination of intra-gay-culture matings of convenience. But until a gay gene is isolated (if ever) it is all idle speculation.
being gay is a lifestyle choice euthanasia for "gay" babies will not reduce the amount of gay men
It is worse than that.
If a "gay gene" is ever isolated, you can be sure that these couples will replenish the supply of new gays by genetically engineering homosexual fetuses.