WASHINGTON - The attorney for an impeached federal judge on trial before the Senate argued Tuesday that Congress was 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 trial that some of the allegations against Judge G. Thomas Porteous were vague or exaggerated. 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 engaged in a persistent pattern of corruption throughout his career, before and after his federal service. Schiff said allowing Porteous, 63, 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 only 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.

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.

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 do not rise to the "high crimes and misdemeanor" standard required by the Constitution for impeachment.

He argues, for example, that the meals, gifts, and favors were business as usual in the New Orleans-area legal community. And he says other charges are exaggerated, including the bankruptcy filing, which Porteous maintains he filed under a false name only to avoid embarrassing publicity.

The Senate plans to vote on the case Wednesday.

The impeachment trial is the first since the 1999 case against 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.