After many months, the mounting campaign to pressure lawmakers and the Defense Department to radically reform the military justice system is hitting a make-or-break moment.

Highly anticipated Senate votes on the reforms are in doubt because of an impasse over the annual defense bill and flaring tensions over divisive changes to Senate rules. The situation has reform advocates intensifying their efforts, fearful that their moment is slipping away.

“We are really doubling down our efforts,” said Paula Coughlin, who was the whistle-blower in the Tailhook scandal and now is an advisory board member at the advocacy organization Protect Our Defenders. “We are not backing down. This is not over.”

Advocates are targeting 13 key undecided senators with intense lobbying campaigns in their states and on Capitol Hill, including enlisting the personal stories of more than 400 military sexual-assault survivors, publishing editorials in key local newspapers nationwide, and reaching out to more than 10,000 followers via email and social media.

At stake are competing reform measures by Sens. Kirsten Gillibrand, D-N.Y., and Claire McCaskill, D-Mo. The Gillibrand amendment would take the decision of whether to prosecute sexual assaults out of the chain of command but keep the legal process within the military. McCaskill is fighting the Gillibrand legislation, proposing a modest alternative package of less controversial reforms.

Votes on both measures were called off before the Senate broke for recess because of an ongoing fight over amendments to the defense authorization bill. With no agreement in sight, prospects for these votes are dimming—and time is rapidly running out for the Senate to act this year.

“If it’s not in the news, it’s not going to make it onto a senator’s desk,” said Coughlin, who authored an editorial making a personal appeal to Sens. Bill Nelson and Marco Rubio of Florida and sent an email letter to supporters, urging them to continue fighting for change.

Both Gillibrand and McCaskill are continuing to push for votes on their measures, and both have introduced their amendments as stand-alone bills. The Gillibrand bill has been filed under a procedure known as Rule 14, which would allow Senate leaders to expedite it and bring it directly to the floor for action on its own.

“For the senator’s part, she is continuing to talk and meet with senators to garner their support,” said Bethany Lesser, a Gillibrand spokeswoman.

But analysts, Senate aides, and even reform advocates acknowledge that it is increasingly unlikely that additional reforms will get votes this year unless they come up as amendments to the embattled defense bill. And some observers cast doubt on that as well.

“The outlook for additional amendments to the National Defense Authorization Act doesn’t look promising,” said Drew Pusateri, a McCaskill spokesman.

Although 53 senators have publicly announced support for Gillibrand’s measure, advocates insist they would have at least 57 votes, and they argue that even an outcome that failed to reach the 60 votes required for passage would help advance the issue next year.

“We really want to see a vote on this bill,” said Greg Jacob, policy director at the Service Women’s Action Network. “That’s pretty critical. Even if it doesn’t pass, having a solid up-or-down vote on the bill is really helpful—because when the bill gets reintroduced, we know who we need to get the next time around.”

There remains a solid band of undeclared lawmakers who see no upside to choosing between assault victims and the Pentagon.

“Obviously, people who are opposed to it or think it is a bad idea might choose to just try to not have the vote, because then you don’t put people on record and you don’t risk having the outcome be what you didn’t want,” said Michael O’Hanlon, a senior fellow with the Brookings Institution.

“I wouldn’t be at all surprised if this is the kind of thing that gets lost in the morass,” he said. “I’m not sure it’s seen as a top-tier issue by the public at large.”