Why New Magic Number for Anti-Trump GOP Forces Is 28

— -- The new magic number: 28.

That’s how many rules panel members anti-Trump forces will need to force a vote on unbinding delegates on the floor of the Republican convention.

Donald Trump has already far-surpassed the 1,237 delegates needed to clinch the GOP nomination. But a last-ditch effort to change the rules and let delegates vote their consciences faces a steep uphill climb in Cleveland. The goal? Take a vote on unbinding the delegates on the convention floor.

Here’s what would need to happen -- and how likely it is:

The Process

The slate of temporary rules must first clear the RNC’s standing rules panel and full RNC next Tuesday and Wednesday. Then, on Thursday and Friday, it will be thrown into a 112-member panel where all bets are off and anything can be changed -- including essentially sidestepping the results of dozens of primaries and caucuses across the country. This is not likely, but just shows the extent of the power of the rules committee.

In order to actually change the temporary rules, a majority of the convention’s rules panel must support the change. But if 25 percent of its members -- just 28 people -- back the amendment, it can make its way to the floor of the full convention. Once on the floor, however, the motion would need to be approved by a majority of the delegates (1,237) to actually take effect.

Rules experts tell ABC News that if anti-Trump forces can get the measure -- a minority report -- to the floor, the convention must either give it an up-or-down vote or take a vote to sidestep it.

ABC News has identified all 112 members of the rules committee, and is working to get in touch with all of them. Of the ones ABC News spoke with, none are particularly gung-ho about implementing a rules change.

What Leaders of This Movement Are Saying

Kendal Unruh, the leader the “Free the Delegates” movement, said on the movement’s weekly conference call last night that she was confident she would be able to garner the 28 votes for a minority report. She told ABC News today that she has 20 members of the committee confirmed to vote, and 8 soft votes -- right on the borderline.

“It is continuing to be the uphill battle I knew it would be,” Unruh said on the call. She said that she has a “strong group” of committee members who have publicly come out for the conscience clause, but there are many other members of the rules committee who support the idea in theory but are afraid to come out publicly. Unruh implored those listening in not to keep all of their faith wrapped up in the outcome of the rules committee.

Another drawback for Free the Delegates: Steve Lonegan, a former Ted Cruz operative whose PAC was working on sponsoring ads and organizing a whip operation at the convention, has cut ties with the group.

What’s Happening Behind The Scenes

Members are getting bombarded with emails from anti-Trump advocates over the last several days, with one rules panel member receiving more than 100 emails before 11 a.m. this morning and another receiving more than 1,000 over the last five days.

“My email is going nuts,” said Judi Schwalbach, a rules panel member from Michigan who opposes a rules change. “I’m generally receiving between 100 and 150 a day. That’s a lot of emails.”

Schwalbach says she’s received two or three calls from the Trump campaign to ensure she does not support a rules change. “I can only imagine the campaign is sitting there saying we can’t let this happen,” she said.

Still, anti-Trump organizers maintain that delegates are already technically free to vote their consciences, even if the rules change fails. “We’re educating the delegates that you’re already unbound and free to vote your conscience,” said Regina Thomson, one of the group’s leaders.