Donald Trump's iron grip on the Republican Party is crumbling in real time.A high-stakes White House summit with Speaker Mike Johnson and top GOP leaders was abruptly canceled Thursday as the President's own party openly revolted against his $1.8 billion 'slush fund' for January 6 rioters.Johnson reportedly refused to sit down with Trump, in a striking act of rebellion by the President's most reliable congressional leader.The meeting was meant to salvage the stalled $70 billion immigration enforcement bill the administration is counting on to fund its deportation operation through 2029. Instead, senators filed out of a tense closed-door session with acting Attorney General Todd Blanche and effectively pronounced the bill dead for the week. Even Trump's most loyal foot soldiers, including Alabama's Katie Britt and Tommy Tuberville, broke ranks to confront Blanche over the prospect of taxpayer money flowing to rioters who wounded police officers at the Capitol on January 6, 2021.Senate Majority Leader John Thune pulled the plug on the votes by sending lawmakers home until June 1, missing Trump's deadline.Thune told reporters the White House 'need to help with this issue, because we have a lot of members who are concerned.' A high-stakes White House summit with Speaker Mike Johnson and top GOP leaders was abruptly cancelled Thursday amid a deepening rift between the President and his own party over a $1.8 billion fund critics are openly denouncing as a 'slush fund' The vast majority of Senate Republicans, including normally reliable Trump loyalists like Senators Katie Britt and Tommy Tuberville, confronted Blanche with grave concerns that the fund could funnel taxpayer money to rioters who assaulted police officers on January 6 , 2021 Senate Majority Leader John Thune pulled the plug on the votes by sending lawmakers home until June 1 A high-stakes White House summit with Speaker Mike Johnson and top GOP leaders was abruptly cancelled Thursday amid a deepening rift between the President and his own partyThune's public break is officially tied to the uproar over Trump's so-called 'slush fund' to reward political allies who claim the Biden Justice Department targeted them.But privately, sources say the majority leader is seething over Trump's decision earlier this week to endorse Ken Paxton over Thune's close ally, John Cornyn, in the Texas Senate GOP primary. When asked if he was losing control of Senate Republican in the Oval Office earlier Thursday, Trump responded: 'I really don't know. I can tell you I only do what's right.'More than half of Senate Republicans privately raised concerns about the fund in the meeting with Blanche, including many who have yet to speak out publicly, sources familiar with the session said. The fund had dropped like 'a bomb in the middle of a pretty well planned out reconciliation bill,' Alaska Senator Lisa Murkowski told reporters.'Do you really think that the American people like the president suing himself, basically, then making a deal that benefits himself with a broad immunity, for not just for IRS dealings but anything else?' said out-going Louisiana Senator Bill Cassidy.Utah Senator John Curtis said flatly: 'I don't like the fund at all.' North Carolina's Thom Tillis branded it a 'payout pot for punks.'Senator Ron Johnson of Wisconsin told CNN: 'Somebody described it as a galactic blunder, and I think that's probably true.'Earlier this week, the Justice Department resolved a $10 billion lawsuit the President had brought against the agency by establishing a $1.8 billion fund for his political allies.It was created to issue formal apologies and monetary relief owed to claimants who were subjected to 'lawfare' under the Biden administration.More than 1,600 January 6 defendants pardoned by Trump are eligible to receive payments from the fund.Two police officers who defended the US Capitol during the 2021 riot have sued Trump in a Washington, DC, district court to block the fund. The GOP Senate majority leader is seething over Trump's decision earlier this week to endorse Ken Paxton over Thune's close ally, John Cornyn, in the Texas Senate GOP primaryFive commissioners will be appointed to oversee the fund and disburse payments to those seeking redress for alleged political persecution under Biden. Trump will have the power to remove those commissioners.Republican frustration is boiling over not just at the $1.8 billion payout, but also at the extraordinary side deal granting Trump and his sons immunity from IRS tax audits.Pennsylvania Representative Brian Fitzpatrick said he had 'never heard' of such an arrangement before, and vowed it would 'of course' be targeted in any legislative effort to kill the fund.'You can't do that,' the Republican told reporters on Wednesday.The GOP backlash over Trump's 'slush fund' comes alongside mounting Republican unease about his $1 billion request for White House security upgrades tied to his planned ballroom.'I know my constituents, and I’m sure many other representatives’ constituents do not want taxpayer money going to a ballroom,' said Fitzpatrick.