FIRST ON FOX: Most of the nation's Republican governors on Tuesday signed on to a letter of support for the massive GOP-crafted budget bill advancing President Donald Trump's second-term agenda on tax cuts, immigration, defense, energy and the debt limit.The letter was sent to the White House as the massive measure, known as Trump's "one big, beautiful bill," is slowly making its way through numerous votes and hurdles in the House of Representatives.And the letter, shared first with Fox News by the Republican Governors Association (RGA), came as Trump made a rare visit Tuesday morning to Capitol Hill to rally Republicans in support of the legislation.INSIDE TRUMP'S URGENT MEETING WITH HOUSE REPUBLICANS"As Republican Governors, we stand UNITED in strong support of your One, Big, Beautiful Bill.This landmark piece of legislation embodies your powerful vision to bring about the next great American revival. It truly delivers on the bold promises all Republicans made to the American people to restore the security, prosperity, and fiscal sanity for our nation," stated the letter, which was signed by 20 of the nation's 27 GOP governors.And the governors argued that "after four long years of tremendous hardship under President Joe Biden and Kamala Harris, the American people cannot wait any longer for Congress to enact the One, Big, Beautiful Bill.""The American people have witnessed the tireless work undertaken by you and your administration to reverse the disastrous consequences of President Bidens failed and often illegal policies," the governors claimed. "You have demonstrated a commitment to using every ounce of Executive authority available to reinstitute fiscal sanity, fight the deep state, secure our borders, and achieve energy dominance."With a fragile, razor-thin majority in the House, GOP leaders in the chamber cannot afford more than a couple of Republicans to hold out against the bill in order to pass it and send it to the Senate. No Democrats in the House are expected to vote for the measure.Upon arriving on Capitol Hill, Trump suggested that any GOP lawmaker who votes against the bill would be "knocked out so fast," as he mentioned a couple of "grandstanders."He urged House Republicans must get his "one big, beautiful bill" done, and added that the GOP is a "very unified party."While Trump's meeting with the House Republicans was kept behind closed doors, two people in the room told Fox News Digital that the president warned House Republicans to not "f--- around" with Medicaid and state and local tax (SALT) deduction caps, two significant points of contention for warring conservative and moderate GOP factions.The Republican governors, in their letter to Trump, said that "we agree with you; Republicans must UNIFY around this unprecedented piece of conservative legislation.""We stand by your side and will support you in any way to ensure this necessary piece of legislation is enacted," they added.The letter was signed by Govs. Kay Ivey of Alabama, Mike Dunleavy of Alaska, Sarah Sanders of Arkansas, Brian Kemp of Georgia (the chair of the RGA), Brad Little of Idaho, Mike Braun of Indiana, Kim Reynolds of Iowa, Jeff Laundry of Louisiana, Tate Reeves of Mississippi, Mike Kehoe of Missouri, Greg Gianforte of Montana, Jim Pillen of Nebraska, Kelly Armstrong of North Dakota, Henry McMaster of South Carolina, Bill Lee of Tennessee, Greg Abbott of Texas, Spencer Cox of Utah, Glenn Youngkin of Virginia, Patrick Morrisey of West Virginia, and Mark Gordon of Wyoming.Fox News' Elizabeth Elkind and Deirdre Heavey contributed to this report.