Senate Democrats argue that Alberto Gonzales is responsible for shaping policies that contributed to the abuse of detainees captured in Afghanistan and Iraq.
"I see a case where Judge Gonzales championed policies that are in fundamental conflict with decades of our laws, of sound military practice, of international law and even of human rights," said Senator Patrick Leahy of Vermont, the top Democrat on the Judiciary Committee.
But Republicans say Judge Gonzales never endorsed torture.
"He has been very emphatic about his personal opposition to torture, and about the opposition of the administration to torture," said Senator Arlen Specter of Pennsylvania, chairman of the Judiciary Committee.
Mr. Specter says Judge Gonzales is well-qualified for the job, after serving as White House lawyer during President Bush' first term.
On Tuesday, Democrats considered, but then abandoned, the idea of raising a procedural hurdle against the nomination to try to scuttle a confirmation vote. They acknowledge they lack the 41 votes in the 100-member body necessary to succeed.
Although many Democrats are expected to oppose the nomination when it comes to a vote, expected on Thursday, Judge Gonzales is expected to be confirmed because the Senate is controlled by President Bush's Republican Party.
Meanwhile, another Bush nominee is expected to be questioned about his role in advising about policy relating to detainees on Wednesday.
U.S. Appeals Court Judge Michael Chertoff, President Bush's choice to head the Homeland Security department, is to testify at a Senate confirmation hearing.
The New York Times has reported that Mr. Chertoff advised the Central Intelligence Agency on the legality of coercive interrogation methods used on terrorism suspects when he served at the Justice Department. The newspaper reported that Mr. Chertoff said some techniques could be legal while advising against others.
But White House spokesman Scott McClellan said the report was inaccurate.
Mr. McClellan said responsibility for interpreting the law is the Justice Department's Office of Legal Counsel. He noted that Mr. Chernoff was head of the Criminal Justice division, where he did not approve any interrogation techniques, but only that he offered his opinion on the matter.