The Republican-led prosecution rested its case on Wednesday for impeaching the attorney general of Texas, Ken Paxton, ending on a central claim: that an Austin real estate investor paid for Mr. Paxton’s home renovations in exchange for favors.

The testimony about countertops and cabinetry — and bills for $121,000 — came on the seventh day of the trial. More than a dozen witnesses, including Mr. Paxton’s most senior aides, described how the Republican attorney general had repeatedly used his office to help the real estate investor, Nate Paul, as he was facing a federal criminal investigation and other legal troubles.

It had appeared, at the start, that the day would focus on another allegation: that Mr. Paul had helped Mr. Paxton conduct an extramarital affair. The prosecution called the woman, Laura Olson, a former staff member to a Republican state senator and a witness whose testimony had been highly anticipated.

Mr. Paxton’s lawyers immediately objected, and Ms. Olson waited around in the Texas Capitol, mostly at a table in the legislative library. She declined a request for comment.

“She’s present but has been deemed unavailable to testify,” said the lieutenant governor, Dan Patrick, who has been acting as the judge in the impeachment trial. He said he had discussed the matter with lawyers for both sides and declined to offer any further explanation. “Both sides have agreed to that statement.”

For much of the trial, Ms. Olson’s key role in the prosecution’s theory of bribery and corruption by Mr. Paxton hovered in the background, eliciting occasional mention but little extended examination.

“It answered that ‘why’ question,” said Jeff Mateer, a former top official under Mr. Paxton, describing in testimony last week what he thought when he learned of Mr. Paul’s purported connection to the extramarital affair.

The trial, before the Republican-dominated State Senate, was expected to conclude by the end of the week. At that point, the 19 Republican and 12 Democratic senators who have been listening to days of testimony and were barred from using their cellphones or from discussing the case, will begin deliberations. A verdict could come shortly after.

A two-thirds vote for conviction — by 21 of the 31 Texas state senators — on any of the articles of impeachment would result in Mr. Paxton’s removal from office. A second two-thirds vote would prevent him from holding public office in the future.

On Wednesday, the House impeachment managers moved to change the rules so that there would be a single vote on each article to both remove Mr. Paxton and bar him from future office. The senators were expected to vote on the motion on Thursday.

The impeachment has deepened rifts within the Republican Party, with backers of Mr. Paxton, who has aligned himself with former President Donald J. Trump, attacking the Republicans supporting the prosecution as insufficiently conservative. Several witnesses started their testimony with examples of their conservative bona fides.

The prosecution’s case, presented primarily by the well-known Houston lawyer Rusty Hardin, has largely rested on the testimony of Mr. Paxton’s own senior aides, most of them political appointees who became whistle-blowers against him in 2020. Several were fired afterward.

The trial centers on allegations that Mr. Paul — a friend and one-time donor of $25,000 to Mr. Paxton’s re-election — assisted Mr. Paxton not only in conducting the extramarital affair but also in paying for renovations to one of Mr. Paxton’s houses. In turn, prosecutors say, Mr. Paxton went to extraordinary lengths to assist Mr. Paul on several different legal matters related to his businesses in 2020. Prosecutors say the exchanges amounted to bribery.

On Wednesday, Mr. Paxton’s former executive assistant, Andrew Wicker, described hearing a conversation between Mr. Paxton and his contractor about expensive changes to plans for renovating his house.

“He mentioned the total of $20,000 for the cabinetry and the countertops,” Mr. Wicker said.

A lawyer for the prosecution, Erin Epley, asked what Mr. Paxton said in response.

“He stated that he would like to move forward,” he said.

And what did the contractor say, she asked.

“He said he would check with Nate,” Mr. Wicker said, adding later that he had heard the phrase repeated at least three times.

In one matter in which Mr. Paxton was said to have aided Mr. Paul, witnesses said that Mr. Paxton pressed his aides to get the attorney general’s office to intervene in a lawsuit between Mr. Paul and a nonprofit known as the Mitte Foundation.

In another matter, Mr. Paxton also pushed to issue an informal opinion about foreclosure sales during the pandemic that, the aides said, ran counter to the office’s policy goal of reopening businesses in the summer of 2020. The opinion helped Mr. Paul, who had properties facing foreclosure, the aides said.

A third matter was the one that finally drove the aides to report their concerns. Mr. Paxton hired an outside lawyer to act as a special prosecutor and to investigate the handling of state and federal law enforcement investigations of Mr. Paul, who claimed that a search warrant on his home and business had been improperly altered.

Top officials in the attorney general’s office, including the head of law enforcement, David Maxwell, had listened to Mr. Paul’s claims but refused to investigate them. Mr. Paxton then turned to an outside counsel.

“General Paxton ordered me to meet with this individual,” Mr. Maxwell recalled during testimony on Friday. “My evaluation of the allegations by Nate Paul were that they were absolutely ludicrous, without merit.”

Mr. Maxwell said that Mr. Paul in fact had wanted the attorney general’s office to interfere with a federal investigation, adding that he had warned Mr. Paxton that by involving himself closely with Mr. Paul, he “was going to get himself indicted.”

Mr. Paxton’s lawyers have argued that Mr. Paxton had the authority to take the actions that he did and that the aides had assumed Mr. Paul was behind certain decisions when he was not.

Mr. Paul, who was not called as a witness by the prosecution, was indicted on federal charges of financial fraud in June, and he pleaded not guilty. Mr. Paxton, who also has not testified, pleaded not guilty to the articles of impeachment at the start of the trial through his lawyer, Tony Buzbee.

In their cross-examinations, Mr. Buzbee and other lawyers for Mr. Paxton have suggested that his aides had jumped to conclusions about his relationship with Mr. Paul and that Mr. Paxton had fired them for refusing to do their jobs and for insubordination.

In responding to the allegation that Mr. Paul had paid for renovations to the home, Mr. Buzbee showed Mr. Wicker pictures of the kitchen, where no updates to the cabinets or countertops appeared to have been made.

The prosecution responded by pointing to documents showing that the first time Mr. Paxton was billed for renovations — an invoice sought more than $121,000 — was the day after the whistle-blowers went to the Federal Bureau of Investigation.

Mr. Buzbee said Mr. Paxton had directed payment the day before.

David Montgomery contributed reporting from Austin.