Donald Trump's march to the election seems unstoppable, but a coalition of anti-Trump Republican delegates are making one last push to get The Donald off the ticket with a so-called 'conscience clause'.

The group, led by Kendal Unruh, a Colorado delegate, wants to change the rules so that delegates aren't forced to pledge their vote towards whichever candidate won their primary. Instead, she wants them to be able to vote with their 'conscience' - essentially against Trump.

'This is a coalition of Kasich, Cruz and Rubio (supporters) and we are all agreeing on one goal, which is: Anybody but Trump,' she told CNN Friday.

Opposition: Colorado delegate Kendal Unruh (left) is leading other delegates in a quest to get GOP convention rules changed so they can back whoever they want - and not be forced to select Donald Trump

Unworried: Trump said that there is 'no mechanism' to make the changes Unruh wants, and that even if there were it would be a 'rebuke' to the millions who voted for him

Unruh made the last-ditch push on Thursday night, organizing a call with dozens of other delegates to work on anti-Trump strategies.

And it seems that the 'Anybody but Trump' slogan is quite literal.

'Nobody has any idea who is going to step in and be the nominee,' she told The Washington Post.

'But we’re not worried about that. We’re just doing that job to make sure that he’s not the face of our party.'

But Trump doesn't appear scared of the threat. He told the Post in a statement: 'I won almost 14 million votes, which is by far more votes than any candidate in the history of the Republican primaries.'

'I have tremendous support and get the biggest crowds by far, and any such move would not only be totally illegal but also a rebuke of the millions of people who feel so strongly about what I am saying.'

But last month rules committee member Curly Haugland told The Daily Caller that the RNC rules do give a mechanism for voting against Trump. In fact, he says, they effectively make every delegate a free agent.

He said that DNC Rule 38 promises: 'No delegate or alternate delegate shall be bound by any attempt of any state or congressional district to impose the unit rule.'

It continues: 'A "unit rule" prohibited by this section means a rule or law under which a delegation at the national convention casts its entire vote as a unit as determined by a majority vote of the delegation.'

That would in effect make every delegate a superdelegate, able to pledge to whoever they choose.

And while the RNC commanded in 2013 that delegates must bind themselves to their state's will, Haugland says that doesn't mean anything because the rules are dissolved and remade with each new convention.

If he's right, that could leave the next convention open for a surprise defeat for Trump.

Rules: Curly Haugland, a rules committee member, says that under DNC rules, delegates are actually able to pledge their backing to whoever they choose - regardless of what their state says

Republican National Committee spokesman Sean Spicer came out in favor of Trump, arguing: 'Donald Trump bested 16 highly qualified candidates and received more primary votes than any candidate in Republican Party history.

'All of the discussion about the RNC Rules Committee acting to undermine the presumptive nominee is silly. There is no organized effort, strategy or leader of this so-called movement. It is nothing more than a media creation and a series of tweets.'

Unruh, who has called her movement 'Free the Delegates 2016', obviously disagrees - as do those following her.

Eric Minor, a delegate from Washington state, told the Post: 'I hear a lot of people saying, "Why doesn’t somebody do something about this?" Well you know what? I’m one of the people who can.

'There’s only 2,400 of us. I’m going to reach out to us and see if there seems to be momentum for this. And if there is, we’ll see where it goes.'

And Steve Lonegan, who is advising the group and raising money through Courageous Conservatives, a super PAC, Courageous Conservatives, said: 'I’ve woken up every day struggling to accept that he’s going to be our candidate.

'He’s spent more time talking about getting Bernie Sanders voters to vote for him than conservatives.

'What do you think he has that Bernie Sanders’s supporters would like? A secret socialist agenda?'

Momentum: Eric Minor is a Washington state delegate. he said that as someone with the power to 'do something' about Trump, he wants to take a chance - and says the movement has 'momentum'

Lonegan's remarks are a sign of a growing split in the GOP, with many of the old guard suspicious of Trump's motives and Republican qualifications, and worried about polls that show him performing poorly against Hillary Clinton in a presidential match-up.

Meanwhile, others are horrified by his remarks - particularly his attacks on Mexican-American judge Judge Gonzalo Curiel, and his call to ban Muslim immigrants to the US, both of which made waves in the past few weeks.

And while the group has a virtually impossible task ahead of them, Lonegan says there is plenty of backing for a change to the rules.

'I will tell you, about every two hours people contact me about how to join this effort,' he told CNN.

'This has never been done before, so there's no textbook on how to do it. So we're building an organic effort, state by state, to convince members of the Rules Committee to sign onto a rule that unbinds the delegates to vote their moral conscience.'

They're not alone. A second group, called Delegates Unbound, plans to buy ad space and TV time to persuade delegates they have the power and authority to vote as they wish, not to adhere to the votes of those in their states, CNN said.

Ultimately, Unruh believes that Trump - who has been moderating his language after meetings with GOP chiefs - is his own worst enemy, and will clinch her success.

'This will be an absolute success once that tranquilizer they sedated Trump with wears off,' she told CNN.