Senate Republicans erupted in frustration Tuesday after President Donald Trump blindsided the GOP conference by endorsing Texas Attorney General Ken Paxton over incumbent Sen. John Cornyn of Texas — a move many fear could hand Democrats a critical Senate seat.The backlash was swift and visceral.Senate Republicans are "livid" with Trump over the move, Punchbowl News reporter Andrew Desiderio reported. Sen. Roger Wicker (R-MS) made that clear without saying a word, walking into a Republican lunch meeting stone-faced, remaining silent for roughly 20 seconds as reporters pressed him for a reaction. Sen. Lisa Murkowski (R-AK) was more blunt, telling reporters she believes Texas is now all but lost to Democrats.Sen. Ron Johnson (R-WI) didn't mince words either — or rather, he couldn't find any."I'm speechless," Johnson told CNN's Manu Raju, adding that he "really" has "no comment."Sen. Lindsey Graham (R-SC) tried to put a positive spin on things, but his math wasn't exactly reassuring for Republicans."You don't have to be a rocket scientist to figure out the pathway for Paxton is there, but it's more uphill, and it will cost more," Graham told Raju.That financial concern is reverberating across the conference. Republicans are now bracing for a costly battle to defend what should be a safe red state, with party money that could otherwise be deployed in competitive races potentially being drained into Texas.Cornyn, who has served in the Senate since 2002, pushed back hard — if carefully — in a statement posted to X."I have worked closely with President Trump through both of his Presidential terms and voted with him more than 99% of the time," Cornyn wrote. "He has consistently called me a friend in this race."Cornyn framed the race as a test of electability, warning voters to choose "a strong nominee to help our GOP candidates down ballot and defeat Talarico in November, or a weak nominee who jeopardizes everything we care about."Trump's endorsement post made clear the decision was personal, not just political. The former president took direct aim at Cornyn, writing that the senator "was not supportive of me when times were tough" and was "very late in backing me" during his 2024 presidential run — a grievance Trump had apparently been nursing for some time. Trump gave Paxton his "Complete and Total Endorsement."Paxton, who survived an impeachment by the Texas House in 2023 and faced years of federal securities fraud charges that were ultimately dropped, has remained one of Trump's most fervent allies. Trump called him a "true MAGA Warrior" who has "ALWAYS delivered for Texas."