Ken Paxton, the Republican attorney general of Texas, pleaded not guilty to charges of corruption and bribery Tuesday on the opening day of his impeachment trial before the State Senate, the first such proceeding for a statewide officer in more than a century.
Mr. Paxton, a third-term incumbent championed by hard-core conservatives and former President Donald J. Trump, is facing trial on 16 articles of impeachment related to accusations, primarily by his former top deputies who became whistle-blowers, that he had abused his office for the benefit of himself and an Austin real estate investor who was said to have assisted Mr. Paxton with home renovations and an extramarital affair.
“Those allegations are flat-out false,” his lead counsel, Tony Buzbee, said, speaking for Mr. Paxton. “The attorney general pleads not guilty.”
The trial has presented a unique test for Republican leaders and lawmakers in the Texas Capitol, where the party exerts overwhelming control, and for the future direction of the party more broadly. Even before the proceedings began, some Republican lawmakers were facing a public pressure campaign backed by wealthy conservative donors, reflecting the influence Mr. Paxton wields as a result of leading conservative legal fights on issues such as immigration, abortion and transgender policies.
Mr. Paxton has sought to strongly align himself with Mr. Trump. But his situation has thus far differed from that of the former president: in Texas, Republican politicians are the ones leading the impeachment against him.
A majority of Republicans in the Texas House joined in a 121-to-23 vote in May to impeach Mr. Paxton. On Tuesday, a majority of Republican Senators began the proceedings by voting to move forward with the trial, dispatching by wide margins multiple attempts by Mr. Paxton’s lawyers to have the entire case dismissed.
When Mr. Paxton’s lawyers put forth a series of unsuccessful motions to dismiss the case, all but one failed by a vote of more than two-thirds of the senators present.
The unsuccessful maneuvering provided early hints into how the trial might take shape: Mr. Paxton had the support of a core of six senators, who voted in favor of each of his lawyers’ motions. But a solid majority of Republicans do not appear to view the trial as a “sham,” as some of his supporters have called it.
Among the state senators seated mostly in silence was Mr. Paxton’s wife, Angela Paxton. According to the rules, she would be counted as present for the purposes of the two-thirds majority needed but barred from voting or joining in any deliberations.
As the votes came down against his lawyers, Mr. Paxton sat in silence at a table to the front of the towering chamber, its seats arranged to resemble a courtroom. Similarly subdued were the gathered spectators. More than a hundred people, mostly supporters of Mr. Paxton, fanned out across the second-floor gallery with shirts proclaiming themselves to be “RINO” hunters — referring to “Republicans in name only” — or supporters of the hard-core conservative group, the True Texas Project.
A large number of the Senate gallery’s 497 seats were empty.
“We thought we’d have more people here,” said Jane Anne Sellars from Frisco in North Texas, a 69-year-old supporter of Mr. Paxton and retired municipal government official. “We were looking for more red.”
Alicia Davis drove five hours to Austin from the East Texas city of Jasper on Monday and was among the first to line up at the Texas Capitol before daybreak on Tuesday morning. “It’s an embarrassment,” she said of the impeachment, which she regarded as unwarranted. Ms. Davis, who is a Republican candidate challenging the Texas House speaker, Dade Phelan, said that she expected the trial would be “a mess.”
A total of 20 articles of impeachment were approved by the Texas House. But the Senate opted to hold off on considering four articles related to Mr. Paxton’s 2015 indictment for securities fraud; those articles could be part of a future proceeding or dismissed at the end of the trial.
Mr. Paxton’s lawyers did succeed in one key motion: preventing their client from being compelled to testify. The lieutenant governor, Dan Patrick, who is acting as a judge in the impeachment trial, ruled that Mr. Paxton could not be forced to testify.
After a lunch break, Mr. Paxton, who has been suspended from office since the House vote, was no longer present in the chamber, a fact that drew immediate notice and an objection from Rusty Hardin, a lawyer for the House Board of Managers, a group of lawmakers who are overseeing the impeachment. Mr. Patrick decided the rules did not require Mr. Paxton to be there.
Mr. Paxton is accused of using his office to benefit the Austin real estate developer Nate Paul, who donated $25,000 to his campaign and, according to the articles of impeachment, paid for his home renovations and helped him engage in an extramarital affair.
“He is not fit to be the attorney general of Texas,” said Representative Andrew Murr, a Republican from rural West Texas, who gave the opening statement for the House impeachment managers. He spoke for about 30 minutes, half the time allotted under the rules.
Tony Buzbee, a lawyer for Mr. Paxton, went through the accusations against Mr. Paxton in far greater detail, providing rebuttals to many of the pieces of evidence and suggesting that it had been the whistle-blowers who acted improperly. He presented the trial as having been born of political retribution by an “establishment” that had been unable to defeat Mr. Paxton at the polls.
“What can be less democratic than 30 people deciding who serves as attorney general of Texas?” said Mr. Buzbee, who successfully represented former Gov. Rick Perry when he was indicted on abuse of power allegations in 2014.
The first witness for the prosecution, Jeff Mateer, was one of the whistle-blowers whose accusations landed Mr. Paxton in political peril. Mr. Mateer, who served for a time as a first assistant attorney general under Mr. Paxton, presented his conservative legal credentials and those of the others who spoke about their bosses’ actions.
“Are you a RINO?” Mr. Mateer was asked by Mr. Hardin.
He said no, emphatically. He described himself as an evangelical Christian. “I was nominated by President Trump to be a federal judge,” Mr. Mateer said, though he was not confirmed.
The trial was expected to last as long as a month. Each side would be given a total of 24 hours for each side to present its evidence and witnesses. A conviction on any of the articles by two-thirds of the Senate, made up of 19 Republicans and 12 Democrats, would be enough to remove him from office. The senators could also vote to bar him from running again.
Among Mr. Paxton’s supporters in the gallery on Tuesday was Steve Hotze, a far-right Republican donor and activist in Houston who has backed conservative causes, including an investigation he funded in advance of the 2020 presidential election that resulted in an assault and, later, indictments. “I came here because there’s nothing more important than the power of your personal presence,” he said. “We already know there are six votes for Paxton — all he needs are five more.”
But, he added, a conviction on any of the articles of impeachment would mean removal of Mr. Paxton from office. “It’s a high hill to climb,” Mr. Hotze said. “It’s a high hill for him.”