(CNN)- A faction of Republicans is pinning a last-ditch effort to stop Donald Trump on a long-shot rules change at the national convention.
Sunday night, GOP operatives trying to drum up an anti-Trump coalition held their second conference call in five days. Roughly 1,000 interested people were on the call, according to organizer Steve Lonegan -- up sharply from the roughly three dozen who were on a similar call last week.
The goal is passing a rule at the Republican National Convention in July that would free delegates to vote their "conscience," negating any binding put in place by states' primaries.
The chorus calling for a miracle to save them from Trump's nomination represents a real angst in the Republican Party about the presumptive nominee, who has suffered weeks of bad headlines and poll data since the end of the GOP primary. While this appears to be the best-organized opposition effort so far to keeping Trump from winning the nomination in Cleveland, doing so is a nearly impossible task.
Still, the Trump campaign went through a major shakeup Monday as Trump ousted his controversial campaign manager, Corey Lewandowski.
It is unclear how many of the people on the phone call Sunday night were actual delegates. Lonegan, a former New Jersey gubernatorial and U.S. Senate candidate, said his "conservative" estimate was about 250.
The group has the backing of Courageous Conservatives PAC, a group which Lonegan serves as spokesman for and originally backed Texas Sen. Ted Cruz. The PAC will serve as a fundraising vehicle, Lonegan said. As of its last filing, the group had just over $4,000 cash on hand and had raised a total of about $360,000 in the primary.
Next steps for the effort include a round of television and radio appearances, and encouraging supporters to make their own outreach through the press and social media.
The biggest focus will be whipping votes on the convention Rules Committee. If the conscience clause proposed by Rules Committee delegate and group organizer Kendal Unruh, of Colorado, can win the backing of 57 Rules Committee members (half plus one), it could go to the floor for a simple majority vote of delegates to govern the convention.
Part of the hope is that by preparing now, delegates will have options if Trump's numbers continue to tank.
"We're walking into a disaster with this guy," said Pat Brady, the former Illinois GOP chairman and a delegate from Illinois for John Kasich, who has begun reaching out to donors and influencers about stopping a Trump nomination and was on the Sunday night call. "If there's a chance we can clean up the mess, I want to be part of it."
But even gathering dozens of convention-goers won't be near enough to get Trump off the ticket.
"I've also heard about Area 51, I've heard about Elvis sightings, I've heard a lot of things," RNC spokesman Sean Spicer said of the Republicans who insist there is a path for derailing Trump's nomination. "The extent of this effort is a bunch of random people tweeting about it, full stop."
Trump says any insurgents are wasting their time.
"There are a couple of guys who are trying to go to Cleveland -- they're trying to get delegates," Trump said at a rally in Las Vegas Saturday. "I thought they already tried that? I mean, I could give you names, but I won't because it's meaningless. First of all, it's illegal. Second of all you can't do it. Third of all, we, not me, we got 14 almost 14 million votes, 14 million votes in the primary system. That's more votes than ever received in the primaries in the history of the Republican Party."
Lonegan insists it's Trump who doesn't understand the primary.
"What planet is this guy from? Who thinks it's illegal not to nominate him -- who says it's a coronation?" Lonegan said.
"Yes, it will cause a gigantic, horrifying explosion of chaos and blah blah blah," said Rick Wilson, a veteran Florida Republican consultant and "Never Trump" leader. "But I think by the time we get to that point, you will see Hillary Clinton has a 15-point lead and Donald Trump will have said more crazy s---. By that point you will have delegates say 'Hey, this a convention, not a suicide pact.'"
Changing the convention rules will likely not only require substantial support on the Rules Committee, it will require a majority of convention delegates to approve -- many of whom were recruited by and support the Trump campaign. And even if delegates sign off on the "conscience" idea, they could still choose Trump on a first ballot.
Another effort being organized by Republican strategists including M. Dane Waters and Eric O'Keefe, "Delegates Unbound," plans to spend $2.5 million to $3.5 million on dual goals of educating delegates about their belief that delegates should be free to vote their beliefs under the current rules, and on a separate goal of stopping Trump.
"Is it a long shot? Of course it's a long shot," Waters said. "It's going to be a difficult road, but I think we're getting to the point that people truly want to do something. Four weeks is an eternity in politics, so anything can happen in the next four weeks."
Brady downplayed the uphill climb, emphasizing that even with little money, all the movement needs is a few key supporters.
"They don't have to raise that much money," Brady said. "This is just an internal RNC lobbying push. You've got 112 people, you've got a lobby," he added, referring to the total number of Rules Committee members.
The anti-Trump forces have yet to show strength outside of small factions, and face skepticism from people who would be key allies. Even delegates that are free to vote their conscience are not planning to switch off Trump.
CNN is in regular touch with more than 50 of the nearly 120 so-called unbound delegates headed to the national convention, and none are changing already stated plans to cast a nominating ballot for Trump.
Kirk Williamson was selected as delegate in Louisiana for Marco Rubio, but by state rules became free to vote for anyone once the Florida senator dropped out of the race. Williamson has coordinated among the Rubio delegates in Louisiana to communicate with the press how they'll vote -- and all five put out a statement saying they'd support Trump once he became the presumptive nominee.
"Nothing's changed, as a matter of fact, everything's kind of quiet and died down since a month ago," Williamson told CNN on Friday. "My personal position and as far as I know, the position of the other Rubio delegates, has not changed. We will vote for the presumptive nominee."
If there were some sort of delegate uprising, Ken Cuccinelli, the delegate chief for Cruz during the senator's presidential bid, would be a logical organizer to seek. Cuccinelli oversaw Cruz's powerful delegate wrangling operation and has been in touch with the hundreds of supporters he's still sending to the convention.
But Cuccinelli maintains that the active role he is keeping in delegate matters is focused on influencing the platform and rules developed at the convention -- not scuttling Trump.
"Beyond that, and to the extent that he has influence, he has not been (no does he plan to become) involved in any effort to circumvent Trump and his presumptive nominee role," Cuccinelli spokeswoman Mallory Rascher said in an email.
Convention Rules Committee delegate and RNC Standing Rules Committee member Solomon Yue, of Oregon is adamant there will be no successful revolt.
He pointed out that roughly four out of five delegates are either Cruz or Trump supporters, who tend to favor anti-Washington sympathies.
"The common denominator of the delegates is anti-establishment, anti-Washington," Yue said. "Never Trump people, they are representing Washington and the establishment. ... I just don't see how this could happen."
Spicer said that if 2012 rules currently governing are re-established by the Rules Committee, the secretary of the convention will record any vote of a bound delegate, including an abstention, as it should be cast by state rules.
CNN delegate analyst and former Rubio campaign aide Will Holley notes the rule governing the convention as of now says the "secretary of the convention shall faithfully announce and record each delegate's vote in accordance with the delegate's obligation under these rules, state law or state party rule" -- and he doesn't buy the argument that abstaining gets around that.
"Some might argue that 'abstention' isn't support for another candidate so it's not in violation, but you'd need to squint pretty hard to see that in the rules, in my opinion," Holley said.
House Speaker Paul Ryan, who will preside over the convention in Cleveland, pledged neutrality in an interview on NBC's "Meet the Press" Sunday.
"It is not my job to tell delegates to do, what not to do, or to weigh in on things like that. They write the rules. They make their decisions," Ryan said.
Bill Kristol, the Weekly Standard editor looking to find a Trump alternative, took inspiration from the Cleveland Cavaliers' NBA championship win Sunday night. "Cleveland Cavaliers: First team to rally from 3-1 to win NBA final. Cleveland Convention: First to free its delegates to win the presidency," Kristol tweeted.
Any plan would almost certainly require backing from a majority of the 2,472 convention delegates total on the public floor of the convention. And a common scenario is delegates deciding to give up their tickets to Cleveland, meaning they would likely be replaced with people favoring Trump regardless, meaning a vote to change the rules would be more difficult.
In Ohio, for example, where all of the delegates are bound to support John Kasich -- two have notified the party that they do not intend to go to the convention now that Trump is the nominee, with one calling herself a conscientious objector and another, Ross McGregor (R-Springfield), citing a traveling conflict.
"I probably had 70 people call and offer to take their places," said Matt Borges, Chairman of the Ohio Republican Party. "And we're all voting for John Kasich anyway; we're bound to John Kasich, so we're going to vote for Kasich on the first ballot — and I don't think there's going to be any second ballot, so none of these people will ever actually cast a vote for Donald Trump."
"We're going to have a great time," Borges said, noting that the delegation plans to honor Ohio Sen. Rob Portman, former House Speaker John Boehner and former Gov. John Kasich and boost enthusiasm for down ballot candidates. "We've got a very, very packed busy schedule of events for our delegation, plus we want to help make sure Cleveland looks good."
Borges added that he feels that he "said my peace during the primaries." He subsequently spoke with Trump for 40 minutes: "We're just moving forward now," he said, stating that he did not feel comfortable revealing what they discussed in a private conversation.
"I'm going to help Trump build an organization in Ohio, because in some ways we are bound to each other," Borges added. "They cannot win without us; and we really would be remiss if we didn't have a strong top of the ticket organization to help us along there."
By Tal Kopan, Tom LoBianco and Maeve Reston, CNN