JEFFERSON CITY, Mo. — Republican lawmakers upset about the Supreme Court decision legalizing gay marriage have advanced measures in about a dozen states this year that could strengthen protections for those who refuse on religious grounds to provide services to same-sex couples. The bills could benefit court clerks, photographers, florists, bakers, wedding-hall operators and others who say gay matrimony goes against their beliefs. For a party already being torn apart by the presidential contest, the state legislative efforts have exposed deep rifts between the GOP’s social conservatives and its pro-business wing.