The House Armed Services Committee took a big and unexpected step toward making women register for the draft as a handful of Republicans joined Democrats on Wednesday night to back a measure whose own sponsor hoped would fail.

“Right now the draft is sexist,” said Rep. Duncan D. Hunter (R-Calif.), who filed an amendment to the House’s annual defense authorization bill to require women between the ages of 18 and 26 to register for the Selective Service, the government agency that keeps records of who is eligible to be conscripted.

Hunter, who is against the Obama administration’s recent policy change allowing women to serve in all combat roles, said he proposed the measure only to start a discussion about the draft. He voted against his amendment, arguing that anyone who favored it would be siding with the administration.

But Hunter’s gamble that committee members would shy away from forcing women into the draft backfired when a slim majority — including five Republicans — opted to endorse the measure by a vote of 32 to 30.

“We have a standards-based force now, and we don’t have a standards-based Selective Service,” Rep. Christopher P. Gibson (R-N.Y.) argued, joining Democrats, all but one of whom also supported the measure.

“We should be willing to support universal conscription,” said Rep. Jackie Speier (D-Calif.). “There’s great merit in recognizing that each of us have an obligation to be willing to serve our country in a time of war.”

But a measure including women in the draft still has a long way to go. It would have to survive a full House vote and then make it through the Senate. It would change a policy that has been in place since 1981, when the Supreme Court ruled that because women could not hold combat jobs, they did not have to register for the draft.

The idea got a boost, however, on Thursday when Senate Armed Services Committee Chairman John McCain (R-Ariz.) said he is open to the idea.

“As far as I’m concerned, if we’re going to put women into combat roles then that’s certainly logical, but I’d like to consult with the committee — all the members of the committee,” he said.

House Speaker Paul D. Ryan (R-Wis.) sounded a more skeptical note, declining to support having women register for the draft.

“We need to take a comprehensive look at the entire Selective Service process, and we shouldn’t just deal with one issue at a time,” Ryan told reporters Thursday.

The underlying defense authorization bill commissions a study of the draft to help answer questions about “what it would mean to keep it, to do away with it, to include females in it,” said the committee’s chairman, Rep. Mac Thornberry (R-Tex.), who voted against the amendment.

“My view is, we need to get those answers,” he said Wednesday night.

The House is expected to vote on the annual defense authorization bill — which now includes the draft registration for women — in mid-May.

If the amendment requiring women to register for the Selective Service survives the process, the policy change could also preempt ongoing court cases about whether excluding women from the draft is discriminatory.

And although the committee voted to change the draft policy for women, the debate Wednesday night revealed that several lawmakers on both sides of the aisle have great reservations about the continued necessity of the draft.

“I would much rather have someone who I know wants to be there, someone who is trained, who is highly capable and who is a professional warrior, to have my back,” said Rep. Tulsi Gabbard (D-Hawaii), a veteran. She voted for the amendment to include women in the draft but said she thought the discussion was “misguided.”

“The bar would have to be dramatically lowered if we were to return to conscription again,” said Rep. Mike Coffman (R-Colo.), who voted against the amendment, remarking that most eligible youths wouldn’t meet the standards for service anyway because of any number of problems, including drug addiction, emotional problems or simply being overweight.

“We have the most elite military that we have today in the history of this country, and I want to keep it that way,” he added.