Sen. Tim Scott called President Trump on Tuesday with a last-ditch plea.
The president was on the verge of publicly endorsing Texas Attorney General Ken Paxton in the state’s tightly contested Republican primary. Scott, a South Caroline Republican who leads the Senate’s campaign arm, urged him to reconsider, according to people familiar with the conversation.
Thirty minutes later, Trump backed Paxton anyway, breaking with Scott and other senior Republicans in Washington, who have long believed that Paxton’s GOP opponent, four-term incumbent Sen. John Cornyn, was a safer bet.
The decision, which came after months of waffling, reflected the president’s renewed conviction that he maintains an iron grip on the party following recent electoral victories, according to people familiar with his thinking. It was also a warning shot to Republicans in Congress that Trump won’t tolerate dissent.
Trump was emboldened by his successful campaign to oust Republican Sen. Bill Cassidy of Louisiana, who lost a GOP primary on Sunday after the president attacked him online and endorsed his opponent. Trump has also repeatedly attacked GOP Rep. Thomas Massie of Kentucky, who is on the ballot Tuesday and has bucked the president in Congress.
The president in recent days has also grown frustrated by a series of setbacks on Capitol Hill—and he was looking for an opportunity to send a message to congressional Republicans, some of the people said.
In recent weeks, GOP lawmakers have publicly raised concerns about his plans to seek $1 billion in federal funding for security-related upgrades tied to the White House ballroom. The Senate’s parliamentarian recently determined that the funding is subject to a 60-vote threshold rather than a simple majority, throwing into question whether Republicans will be able to fast-track a vote for the project.
GOP lawmakers have also balked at Trump’s push to end the filibuster to pass legislation requiring proof of citizenship to register to vote. Senate Majority Leader John Thune (R., S.D.) this week said he is “not a big fan” of Trump’s recently announced $1.8 billion fund for people who claim to have been victims of so-called weaponization by the government.
“I think the timing of this is as much about President Trump sending a message to John Thune as the leader of the Senate as it is about an endorsement of Ken Paxton,” said Steve Bannon, a Trump ally and Paxton supporter.
Trump and Thune spoke on Monday, and the president didn’t tell the majority leader that he planned to make an endorsement in the race, people familiar with the conversation said. Instead, an aggravated Trump asked Thune to fire the Senate parliamentarian, the people said, after her decision complicated his efforts to secure federal funding for the ballroom project.
Senate Republican leadership thought up until early Tuesday that Trump wouldn’t make an endorsement, a person familiar with the matter said.
Trump’s endorsement of Paxton, which came after he showed off the White House ballroom construction to reporters, singled out the Texas attorney general for his support for ending the filibuster and for the Save America Act, which would require proof of citizenship to register to vote.
Shortly after 2 p.m. on Tuesday, Thune faced a throng of reporters at his weekly press conference in the Senate. Asked if had gotten a heads up from Trump, Thune said he had found out “like everyone else.” Thune stood by his support for Cornyn.
Some Senate Republicans argue that Cornyn is the stronger of the two Republican candidates and that Paxton could be at risk of losing to Talarico. Paxton has $2.3 million in cash to spend, compared with Cornyn’s $4.1 million. Talarico has a war chest of $9.8 million, but he will nonetheless face an uphill battle in the state. A Democrat hasn’t won statewide there since 1994.
Some Republicans worry Trump’s endorsement of Paxton will make an already expensive race even more costly, and they point to Paxton’s personal and political scandals. Texas Republicans continue to support Paxton for his conservative policies, and they argue he has been unfairly targeted.
Trump’s endorsement creates an awkward situation for the National Republican Senatorial Committee, which has attacked Paxton over everything from details of his divorce to impeachment by the Republican-controlled Texas House.
Last year NRSC spokeswoman Joanna Rodriguez called Paxton’s actions “truly repulsive and disgusting.” On Tuesday, NRSC officials didn’t respond to questions about the group’s future support for Cornyn.
Write to Natalie Andrews at natalie.andrews@wsj.com, Meridith McGraw at Meridith.McGraw@WSJ.com and Elizabeth Findell at elizabeth.findell@wsj.com