The attorney for a federal judge facing a rare impeachment trial in the Senate argued Tuesday that Congress is pursuing unconstitutional charges against his client and would be breaking with two centuries of precedent by removing him from office.

Defense attorney Jonathan Turley told senators assembled in the chamber for the historic proceeding that some of the allegations against Judge G. Thomas Porteous are vague. Others, he said, involve conduct that occurred before Porteous was appointed to the federal bench.

“In the history of this republic, no one has ever been removed from office on the basis of pre-federal conduct,” Turley said, urging the senators to dismiss some of the most serious charges.

The lead House prosecutor, Rep. Adam Schiff, D-Calif., responded that Porteous’ actions throughout his career show a persistent pattern of corruption before and after his federal service. Schiff said allowing Porteous to remain on the bench would erode public confidence in the courts and make a mockery of the federal judiciary.

“He must be removed,” Schiff said.

The arguments came as the Senate began the final stage of the case against Porteous, a U.S. district court judge from Louisiana who could become just the eighth federal judge to be removed from office.

The House voted unanimously in March to bring four articles of impeachment against him. A two-thirds Senate vote is needed to convict. The proceeding is just the 16th judicial impeachment trial before the Senate.

House prosecutors allege that Porteous was racking up debt as he struggled with drinking and gambling problems. They say he began accepting cash, meals, trips and other favors from people with business before his court, beginning as a state judge in the 1980s and continuing after he was appointed to the federal bench by President Bill Clinton in 1994.

During previous evidence-gathering hearings, two attorneys who once worked with Porteous said they gave him thousands of dollars in cash, including about $2,000 stuffed in an envelope in 1999, just before Porteous decided a major civil case in their client’s favor. They also said they paid for meals, trips and part of a bachelor party for one of Porteous’ sons in Las Vegas, including a lap dance at a strip club.

One of the attorneys said they paid the judge in cash to avoid a paper trail and that some of the transactions probably amounted to an illegal kickback scheme. Another said Porteous’ requests grew so common that he started trying to dodge the judge.

Another witness, New Orleans bail bondsman Louis Marcotte, described a long-standing relationship in which Marcotte and his employees routinely took Porteous to lavish meals at French Quarter restaurants, repaired his automobiles, washed and filled his cars with gas, and took him on trips. In return, Porteous manipulated bond amounts for defendants to give Marcotte the highest fees possible, said Marcotte, who served 18 months in prison on related corruption charges.

Porteous, who sat with his attorneys Tuesday before the chamber, also stands accused of filing for bankruptcy under a false name and lying to the Senate during his judicial confirmation.

Turley has argued that Porteous may have made poor decisions but that his actions don’t rise to the “high crimes and misdemeanor” standard required by the Constitution for impeachment. He has sought to portray much of the judge’s behavior as business as usual in the New Orleans-area legal community.

The impeachment trial is the first since the 1999 case against former President Bill Clinton, who was acquitted.

Porteous would be the first judge to be impeached and convicted since 1989, when two judges — Walter Nixon of Mississippi and Alcee L. Hastings of Florida — were removed from office. Hastings went on to win a seat in Congress, where he still serves.

The Senate is planning to vote on the case Wednesday morning.