The historic impeachment of the attorney general of Texas, Ken Paxton, plunged Republicans on Sunday into a fight over whether to banish one of their own in America’s biggest red state after years of scandal and criminal accusations that will now be at the center of a trial in the state Senate.

Mr. Paxton said he has “full confidence” as he awaits judgment from the Senate, where his conservative allies include his wife, state Senator Angela Paxton, who has not said whether she will recuse herself from the proceedings to determine whether her husband will be permanently removed from office.

For now, Texas’ three-term attorney general is immediately suspended after the state House of Representatives on Saturday impeached Mr. Paxton on 20 articles that included bribery and abuse of public trust.

The decisive 121-23 vote amounted to a clear rebuke from the GOP-controlled chamber after nearly a decade of Republican lawmakers taking a mostly muted stance on Mr. Paxton’s alleged misdeeds, which include felony securities fraud charges from 2015 and an ongoing FBI investigation into corruption accusations.

He is just the third sitting official in Texas’ nearly 200-year history to have been impeached.

“No one person should be above the law, least not the top law officer of the state of Texas,” said state representative David Spiller, a Republican who was part of a House investigative committee that this week revealed it had quietly been looking into Mr. Paxton for months.

Governor Abbott has remained silent about Mr. Paxton all week , including after Saturday’s impeachment. Mr. Abbott, who was the state’s attorney general prior to Mr. Paxton’s taking the job in 2015, has the power to appoint a temporary replacement pending the outcome in the Senate trial.

It is not yet clear when the Senate trial will take place. Final removal of Mr. Paxton would require a two-thirds vote in the Senate, where Republican members are generally aligned with the party’s hard right. The Senate is led by Dan Patrick, the lieutenant governor who has served as state chairman for President Trump’s campaigns in Texas.

Before the vote Saturday, Mr. Trump and Senator Cruz came to Mr. Paxton’s defense, with the senator calling the impeachment process “a travesty” and saying the attorney general’s legal troubles should be left to the courts.

“Free Ken Paxton,” Mr. Trump wrote on his social media platform Truth Social, warning that if House Republicans proceeded with the impeachment, “I will fight you.”

Mr. Paxton, 60, decried the outcome in the House moments after scores of his fellow partisans voted for impeachment. His office pointed to internal reports that found no wrongdoing.

“The ugly spectacle in the Texas House today confirmed the outrageous impeachment plot against me was never meant to be fair or just,” Mr. Paxton said. “It was a politically motivated sham from the beginning.”

Lawmakers allied with Mr. Paxton tried to discredit the investigation by noting that hired investigators, not panel members, interviewed witnesses. They also said several of the investigators had voted in Democratic primaries, tainting the impeachment, and that Republican legislators had too little time to review evidence.

“I perceive it could be political weaponization,” one of the House’s most conservative members, Representative Tony Tinderholt, said before the vote. Another, John Smithee compared the proceeding to “a Saturday mob out for an afternoon lynching.”

A political science professor at Rice University, Mark P. Jones, said the swift move to impeach kept Mr. Paxton from rallying significant support and allowed quietly frustrated Republicans to come together.

“If you ask most Republicans privately, they feel Paxton is an embarrassment. But most were too afraid of the base to oppose him,” Mr. Jones said. By voting as a large bloc, he added, the lawmakers gained political cover.

To Mr. Paxton’s longstanding detractors, however, the rebuke was years overdue.

In 2014, he admitted to violating Texas securities law, and a year later was indicted on securities fraud charges in his hometown near Dallas, accused of defrauding investors in a tech startup. He pleaded not guilty to two felony counts carrying a potential sentence of five to 99 years.

He opened a legal defense fund and accepted $100,000 from an executive whose company was under investigation by Mr. Paxton’s office for Medicaid fraud. An additional $50,000 was donated by an Arizona retiree whose son Mr. Paxton later hired to a high-ranking job but soon was fired after displaying child pornography in a meeting. In 2020, Mr. Paxton intervened in a Colorado mountain community where a Texas donor and college classmate faced removal from his lakeside home under coronavirus orders.

What ultimately unleashed the impeachment push, however, was Mr. Paxton’s relationship with Austin real estate developer Nate Paul.

In 2020, eight top aides told the FBI they were concerned Mr. Paxton was misusing his office to help Mr. Paul over the developer’s unproven claims about an elaborate conspiracy to steal $200 million of his properties. The FBI searched Mr. Paul’s home in 2019, but he has not been charged and denies wrongdoing. Mr. Paxton also told staff members he had an affair with a woman who, it later emerged, worked for Mr. Paul.

The impeachment accuses Mr. Paxton of attempting to interfere in foreclosure lawsuits and issuing legal opinions to benefit Mr. Paul. The bribery charges included in the impeachment allege Mr. Paul employed the woman with whom Mr. Paxton had an affair in exchange for legal help and that he paid for expensive renovations to the attorney general’s home. A senior lawyer for Mr. Paxton’s office, Chris Hilton, said Friday that the attorney general paid for all repairs and renovations.

Other charges, including lying to investigators, date back to Mr. Paxton’s still-pending securities fraud indictment.

Four aides who reported Mr. Paxton to the FBI later sued under Texas’ whistleblower law, and in February he agreed to settle the case for $3.3 million. The House committee said the probe was sparked by Mr. Paxton seeking legislative approval for the payout.

“But for Paxton’s own request for a taxpayer-funded settlement over his wrongful conduct, Paxton would not be facing impeachment,” the panel said.