Ken Paxton, the embattled attorney general of Texas, survived an impeachment vote in the State Senate over the weekend, but the case is far from behind him: The U.S. Justice Department still has an open investigation over many of the same allegations of corruption and abuse of office.

And in October, Mr. Paxton’s lawyers will be in court with state prosecutors to set a trial date for his pending indictment on two counts of securities fraud, an eight-year-old case that the senators did not take up directly in their acquittal vote on Saturday.

His lawyer, Dan Cogdell, predicted that the securities case would be quickly dealt with.

“They ought to dismiss it, and if they don’t dismiss it, we’ll try and beat them there just like we beat them here,” he said on Saturday of the state charges. He was less willing to make a prediction about the investigation by the Federal Bureau of Investigation and the Justice Department’s public integrity section. “I don’t speak to the F.B.I. — I try not to,” he said.

Mr. Paxton has faced a cloud of legal troubles since he was sworn in as attorney general in 2015, replacing Greg Abbott, who is now governor. He has been twice re-elected, in part by aligning himself with the right-leaning politics championed by former President Donald J. Trump. Voters delivered comfortable victories to Mr. Paxton even after his indictment and after several of his top aides came forward with claims that he had abused his office by helping a wealthy donor, the subject of the recent attempt to oust him from office.

But legal experts said that after the Senate acquittal, Mr. Paxton could face a more serious legal threat by the pending Justice Department investigation. State prosecutors said in February that the department is looking into allegations made by the whistle-blowers that Mr. Paxton extended unusual help from his office to benefit a political donor, Nate Paul, an Austin real estate investor, and that Mr. Paul had paid for renovations to his house and employed a woman he was having an affair with.

The case was taken over by the Justice Department’s public integrity section in Washington, the state prosecutors said, after the U.S. Attorney’s Office for the Western District of Texas had been recused. The reason for the recusal was not explained, and the department has not responded to inquiries.

Federal agents in Texas were accused by Mr. Paul of misconduct, and it was Mr. Paul’s successful attempt to get them investigated by Mr. Paxton that formed a major part of the whistle-blowers’ allegations. The takeover by agents in Washington may have been done to avoid the appearance of any conflict in the Texas office.

Federal investigators are likely to rely on evidence and testimony that was made public during the recent legislative hearings. More than a dozen witnesses described how Mr. Paxton repeatedly used his office to help Mr. Paul.

In June, federal prosecutors charged Mr. Paul with making false statements to financial institutions by exaggerating the value of his assets, telling mortgage companies and credit unions that he had more money than he did. The case could provide an incentive to Mr. Paul to cooperate with the federal government in the investigation of Mr. Paxton, legal analysts said.

But time may be on Mr. Paxton’s side. Federal investigations often drag on for months and years, and Mr. Paxton’s lawyers could be counting on the possibility that a new Republican administration might be less inclined to pursue the case.

Mr. Paxton and his supporters have long sought to portray the cases against him as a plot by political opponents — the Biden administration, liberals in Texas and moderate Republicans in the Texas House — to undermine the party’s conservative faction.

On Monday, Lt. Gov. Dan Patrick, a sharp critic of the impeachment case sent to the State Senate by the Texas House, called on the state auditor to determine how much public money had been spent on the proceedings.

“To be clear, the goal is to determine the absolute total cost to the state of preparing for and conducting this trial from the beginning through its conclusion,” Mr. Patrick said in a statement.

Also on Monday, Mr. Paxton’s wife, State Senator Angela Paxton, broke her silence after days of watching without comment as House managers brought evidence against her husband, including an attempt to call as a witness the woman with whom her husband was having an extramarital relationship. Ms. Paxton attended the hearings, but was not allowed to deliberate or vote.

“This was a monumental moment in Texas history, for me as a senator, and of course personally as well,” she said in a statement. “Had I been allowed to vote, I would have cast my vote with those who acquitted on each and every article.”

In the securities fraud case pending in Harris County, Mr. Paxton faces charges that he solicited clients and investors for two companies while he was a member of the Texas House. Prosecutors said he misled investors in a technology company, Servergy Inc., by soliciting more than $600,000 in investments in 2011 but misrepresenting himself as an investor in the company and failing to disclose that he was making a commission on the investments.

Mark Jones, a political science professor at Rice University who has followed the cases closely, said that people accused of similar charges are often penalized with fines and almost never end up going to trial. “I think it’s reasonable to make the case that if it hadn’t been the attorney general, those charges would have never been filed,” Mr. Jones said.

Pretrial disagreements have led to years of delays.

Mr. Paxton’s next real test will be at the polls, when he makes a case for re-election in 2026.

He has remained popular with his base, even during the impeachment proceedings. According to a recent poll by the Texas Politics Project at the University of Texas at Austin, only 24 percent of Republican respondents agreed that there was enough evidence that he engaged in wrongdoing to justify his removal. A larger proportion said that they either disagreed, had no opinion or did not know.

J. David Goodman contributed reporting. Susan C. Beachy contributed research.