More good news for Trump: Billionaire Koch brothers will NOT spend money attacking frontrunner in bid to take him out of Republican White House race

The Koch brothers, the most powerful conservative mega donors in the United States, will not use their $400 million political arsenal to block Republican front-runner Donald Trump's path to the presidential nomination, a spokesman told Reuters on Wednesday.

'We have no plans to get involved in the primary,' said James Davis, spokesman for Freedom Partners, the Charles and David Koch's political umbrella group. 

He would not elaborate on what the billionaire industrialists' strategy would be for the Nov. 8 general election to succeed Democratic President Barack Obama.

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No bad day for Trump: Donors and media reports have speculated since a Koch brothers summit in January that they would launch a 'Trump Intervention,' but that is now off the cards

Donors and media reports have speculated since a Koch brothers summit in January that they would launch a 'Trump Intervention,' which would involve deploying the Kochs' vast political network to target the billionaire businessman and former reality TV star in hopes of removing him from the Republican race.

Many Republican party elites and business backers are eager to see Trump, a political outsider who has tapped into America's rising anti-establishment sentiment, fail in his bid for the nomination.

But with Trump racking up a series of sizeable wins in the early nominating contests, there is a growing sense of inevitability he will win the party's mantle.

Three sources close to the Koch brothers, who oppose Trump's protectionist trade rhetoric and views on immigration, said the Kochs were concerned they had not yet seen any attack on Trump stick.

The brothers are also smarting from the millions they pumped into the 2012 Republican presidential bids of Newt Gingrich and Mitt Romney, only to see both candidacies fail, the sources said.

The move will come as a blow to some within the Republican establishment who had been hoping to enlist significant financial support in an effort to stop Trump.

The influence of the Koch brothers, on top of the strength of their arsenal, would have been a significant boost to any 'dump Trump' insurgency.

But there is increasing feeling within the party that it woke up to the threat posed by Trump far too late to be able to counter it.

That was tacitly acknowledged by Mitch McConnell, who the New York Times reported has given permission to senators to run advertising distancing themselves from Trump in the run-up to elections.

Meanwhile Paul Ryan, who as House Speaker is the most senior figure in the party and will chare the July convention in Cleveland, Ohio, which will anoint the White House candidate denounced Trump for not more forcefully disavowing an endorsement from Ku Klux Klan leader David Duke.

'This party does not prey on people’s prejudices,' Ryan said.

Opposed in principle: Koch brothers David (left) and Charles (right) do not agree with Trump on trade or immigration but sources say they are concerned no attacks on the billionaire have stuck

When Trump celebrated his Super Tuesday victories and took questions from reporters in Florida, he was asked about the push back he was receiving from Ryan and others on Capitol Hill.

'I'm going to get along great with Congress, OK?' Trump said. 'Paul Ryan, I don't know him well, but I'm sure I'm going to get along great with him.'

'And if I don't?' Trump said. 'He's gonna have to pay a big price, OK?'

And Lindsey Graham, the South Carolina senator who dropped his own White House bid, has also called for action against Trump, saying that he would back Ted Cruz.

'Ted Cruz is not my favorite by any means,' he told CBS. 'But we may be in a position where rallying around Ted Cruz is the only way to stop Donald Trump, and I'm not so sure that would work.'

The comments came as the #NeverTrump hashtag spread across Twitter.

Romney, the Republican nominee four years ago, announced plans to speak on the 'state of the 2016 presidential race' Thursday in Utah. 

The former Massachusetts governor has moved aggressively to take on Trump in recent days, saying the billionaire's unreleased tax returns might contain 'bombshells'.

However, he was not expected to endorse a candidate or announce a late entry into the race himself.

The best hope the establishment have for defeating Trump is to keep him from getting a majority of delegates in the primary cycle so that the convention is used to determine the winner.

However such a move - known as a brokered convention - would be hugely risky. The last Republican brokered convention was in 1948.

And Franklin D. Roosevelt is the last presidential candidate to have won an election after a brokered convention.