The report represents a comprehensive review of the division’s litigation activity in the Bush administration. When compared with the Clinton administration, its findings show a significant drop in the enforcement of several major antidiscrimination and voting rights laws. For example, lawsuits brought by the division to enforce laws prohibiting race or sex discrimination in employment fell from about 11 per year under President Bill Clinton to about 6 per year under President George W. Bush.

The study also found a sharp decline in enforcement of a section of the Voting Rights Act that prohibits electoral rules with discriminatory effects, from more than four cases a year under Mr. Clinton to fewer than two cases a year under Mr. Bush.

Joseph Rich, a civil rights lawyer who has been invited by Democrats to testify and was among those given an early copy of the report, said it provided hard data that the division was politicized in the Bush years.

The report “confirms the types of problems we have been discussing for several years, particularly with respect to the enforcement record of the Bush administration,” said Mr. Rich, who spent 37 years in the Civil Rights Division and led its voting rights section.

Republicans have signaled that they will use the hearing to accuse the Obama administration of politicizing the division in its own way. They are focusing on a decision to downgrade voter-intimidation charges stemming from an incident in the 2008 election in which two members of the New Black Panther Party stood outside a Philadelphia precinct in militia uniforms, one of them holding a night stick. The charges were brought in the final days of the Bush administration and were downgraded and partially dropped in May.