“What’s needed is a neutral and unbiased individual to review the documents,” said Nan Aron, founder and president of the Alliance for Justice, a liberal advocacy group. “That is not Bill Burck, whose loyalty lies with Brett Kavanaugh and the Bush administration.”

During his long career in public service — as a lawyer working for Kenneth W. Starr, the independent counsel who investigated former President Bill Clinton, as an associate White House counsel to Mr. Bush and later as staff secretary from 2003 to 2006 — Judge Kavanaugh has left an especially voluminous paper trail.

On Thursday, Mr. Burck wrote to Senator Charles E. Grassley of Iowa, the chairman of the Judiciary Committee, and enclosed what he described as an “initial production” of more than 125,000 pages of records from Judge Kavanaugh’s stint as the associate White House counsel. Mr. Grassley had requested those records.

But Republicans have rebuffed Democrats’ repeated demands for access to emails and other records from the three years that Judge Kavanaugh spent as staff secretary — a job that the judge himself has said was “the most interesting and informative for me” as preparation for his current role on the federal appeals court.