One possible option exists for proponents, adding the gay rights bill to the annual defense policy measure that the Senate will consider later this month and force the House to reject the popular legislation.
Through three days of Senate debate, opponents of the legislation remained mute, with no lawmaker speaking out. That changed on Thursday, as Republican Sen. Dan Coats of Indiana said the legislation would force employers to violate their religious beliefs.
"There's two types of discrimination here we're dealing with, and one of those goes to the very fundamental right granted to every American through our Constitution, a cherished value of freedom of expression and religion," Coats said.
Current federal law prohibits discrimination on the basis of sex, race and national origin. But it doesn't stop an employer from firing or refusing to hire workers because they are gay, lesbian, bisexual or transgender.
The bill would bar employers with 15 or more workers from using a person's sexual orientation or gender identity as the basis for making employment decisions, including hiring, firing, compensation or promotion. It would exempt religious institutions and the military.
The Senate approved an amendment from Republican Sens. Rob Portman of Ohio and Kelly Ayotte of New Hampshire that would prevent federal, state and local governments from retaliating against religious groups that are exempt from the law.
The Senate rejected an amendment sponsored by Republican Sen. Pat Toomey of Pennsylvania that would have expanded the number of groups that are covered under the religious exemption.
Portman, Ayotte and Toomey voted for the legislation.
The first openly gay senator, Democrat Tammy Baldwin of Wisconsin, called the vote a "tremendous milestone" that she will always remember throughout her time in the Senate.
Sens. Tom Coburn, R-Okla., John Barrasso, R-Wyo., and Jeff Sessions, R-Ala., did not vote. Sen. Bob Casey, D-Pa., a supporter of the bill, said his wife underwent heart surgery this week and he was unable to make the vote.
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