He said on ABC's "Good Morning America" Friday the same thing is happening with the issue of marriage that happened with gays' service in the military.
Changes in attitudes by military leaders, those in the service and the public allowed the repeal by Congress of the "don't ask, don't tell" policy that will eventually allow gays to serve openly in the military.
Gay marriage is still not legal in most states. President Barack Obama recently said his feelings on the gay marriage issue are evolving, but he still believes in allowing strong civil unions that provide certain protections and legal rights that married couples have.