WASHINGTON — Rod J. Rosenstein, the deputy attorney general, has asked federal prosecutors to help review the government documents of Judge Brett M. Kavanaugh, President Trump’s Supreme Court nominee, according to a letter obtained by The New York Times on Wednesday.

Mr. Rosenstein’s request was an unusual insertion of politics into federal law enforcement. While the Justice Department has helped work on previous Supreme Court nominations, department lawyers in Washington typically carry out that task, not prosecutors who pursue criminal investigations nationwide.

But in an email sent this week to the nation’s 93 United States attorneys, Mr. Rosenstein asked each office to provide up to three federal prosecutors “who can make this important project a priority for the next several weeks.” Names were to be submitted to Mr. Rosenstein’s office by the end of Wednesday.

Mr. Trump nominated Judge Kavanaugh on Monday to replace Justice Anthony M. Kennedy, who is retiring. In years of public service — including work for the independent counsel investigation of President Bill Clinton, on the 2000 Florida recount and as a White House aide to George W. Bush — Judge Kavanaugh generated a lengthy paper trail. That had Senator Mitch McConnell of Kentucky, the majority leader, privately expressing concern that it might be used against him in his Senate confirmation hearings.