Donald Trump listens to a question during a town-hall event. Darren McCollester/Getty Images It was a terrible, horrible, no good, very bad week for Donald Trump — one that allowed the "Never Trump" movement to emerge from the ashes with some much-needed newfound energy.

The presumptive Republican nominee prompted sharp criticism from members within his own party when he publicly argued that a US federal judge’s Mexican heritage made him unfit to oversee fraud cases involving Trump University.

The comments were strongly rebuked by House Speaker Paul Ryan and condemned from all sides of the party. Senate Majority Leader Mitch McConnell went as far as to recommend the New York businessman “use a script more often” and pleaded with him to “change direction.”

And as the week went on, the Never Trump movement — the segment within the party that coalesced midway through the primary to prevent his nomination, but to no avail — grew louder and louder.

On Tuesday, Steve Lonegan, former New Jersey chairman for Ted Cruz's 2016 White House bid, said delegates attending the Republican National Convention in Cleveland have a "moral obligation" to "break the rules" and stop Donald Trump from securing the nomination.

One day later, conservative talk-show host Hugh Hewitt echoed Lonegan, imploring the GOP to examine what it would take to change the rules so that it could dump Trump at the convention. He likened the billionaire to “stage-four cancer” destroying the health of the Republican Party.

Tim Miller, the communications director of an anti-Trump PAC and former adviser to Jeb Bush's presidential campaign, wrote on Twitter that the GOP should “amend the rules to allow each delegate to make an objection of conscience to Trump on the 1st ballot.”

And in Politico's Playbook newsletter, Mike Allen said the scenario was “highly unlikely to happen,” but said it was “no longer unthinkable that establishment Republicans” may “seriously ponder a movement to deny him the nomination.”

Republican presidential candidate Donald Trump speaks to guests during a rally at Macomb Community College on March 4, 2016, in Warren, Michigan. Scott Olson/Getty Images In conversations with Business Insider, some of the movement’s top leaders said Trump’s comments had ignited new behind-the-scenes efforts to stop the real-estate mogul from becoming the party’s standard-bearer.

“I have had a number of donors and elected officials call me in the past 48 hours who were very adamant just two weeks ago that I should get on board with Trump. Now they are all looking for options realizing they really can’t control Trump,” said Erick Erickson, the former editor-in-chief of RedState and founder of the conservative website The Resurgent.

“There are three different groups all exploring options on delegates,” he added. “They are in separate orbits and have not combined, but are now starting to talk to each other and make connections. One of those groups consists of Rules Committee members.”

Republican strategist Rick Wilson, another "Never Trumper," told Business Insider it was hard for him to imagine a scenario in which the billionaire isn’t challenged.

“Barring some miraculous change in Trump's character and discipline, it's practically inevitable,” he said. “The party is terrified, from dogcatchers to US senators, and the sense it needs to happen grows by the day.”

“I know a few folks who were trying to set up the floor fight before he got to 1,237, and they've gotten very active again,” Wilson added, referring to the number of delegates needed to clinch the nomination on the first ballot.

Wilson noted that 2012 nominee Mitt Romney, Texas Sen. Ted Cruz, and Wisconsin Gov. Scott Walker had all been floated as possible candidates the party could nominate.

Republican presidential candidate Donald Trump yells into the crowd at the conclusion of a campaign rally at Lenoir-Rhyne University, March 14, 2016, in Hickory, North Carolina. Sean Rayford/Getty Images Trump's supporters, however, laughed off the talk.

Asked for comment on the movement’s latest efforts, conservative provocateur Ann Coulter joked that the Never Trump crowd “will figure out what’s happening about 10 minutes into President Trump’s inaugural address.”

“That would be hilarious!” she wrote in a follow-up email when asked if she thought GOP insiders might actually try to strip the nomination from Trump.

Even some prominent conservative figures averse to Trump's nomination cast doubt on the new plans.

"I haven't heard anything more concrete than idle and wishful musings!" Rich Lowry, the editor of National Review, told Business Insider.

Romney said in a Friday CNN appearance a rules change was "not realistic." "I think changing the rules and denying [Trump] the nomination is not likely to happen," the former Massachusetts governor said.

Virginia Republican National Committeeman Morton Blackwell, a former Cruz supporter who sits on the RNC Standing Committee on Rules and now supports the presumptive nominee, also dismissed the idea of stopping Trump through a rules switch as a “nonstarter” proposition.

“This stuff, obviously is titillating … but it’s not a serious thing,” he told Business Insider in a phone interview. “If the rules were changed in order to facilitate the nomination of somebody other than Trump, it would be only after a ferocious battle at the Rules Committee in Cleveland, followed by a ferocious battle on the floor of the convention.”

He continued, explaining:

That has to be debated on the floor of the convention. It would be a terribly ugly fight. I don’t think that those who want to change the rules will change the rules, but if they did manage to change the rules, it would badly split the party.

Blackwell said that he had faith “there are enough people of good sense within the Republican apparatus” to ensure “it will not happen.”

“It’s a fantasy,” he insisted. The veteran RNC committeeman, however, left the tiniest sliver of possibility open that the unexpected could happen.

“Well, it’s hard to say never,” he said.

“I’ll put it this way," he added. "Rounded off to the nearest whole digit, it’s a zero chance. Maybe 0.00001%. It’s not going to happen.”