Sen. Dianne Feinstein has called for an inquiry into why former Attorney General Loretta Lynch directed then-FBI director James Comey to refer to the Clinton email investigation as a “matter.”

That’s an encouraging development, as law enforcement should never be a playing field for partisan politics.

The words that triggered Feinstein’s concern may be just the tip of an iceberg. In his June 8 testimony to the Senate Select Committee on Intelligence, Comey said it gave him a “queasy” feeling that the attorney general was asking him to use language that “tracked the way the campaign was talking about the FBI’s work.” He called it “concerning.”

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California’s descent to socialism He wasn’t alone in his concerns. On Oct. 3, House Judiciary Committee Chairman Bob Goodlatte sent a letter to Lynch asking about immunity agreements with key witnesses in the FBI’s investigation into Clinton’s exclusive use of a private email server as secretary of state.

In December 2015, the Justice Department signed two immunity agreements with Bryan Pagliano, the State Department technician who set up Clinton’s server. The following May, immunity was granted to Paul Combetta, the information technology contractor who deleted archived Clinton emails that were under subpoena. A month later, the DOJ granted immunity to former State Department information resources manager John Bentel, and to Heather Samuelson and Cheryl Mills, attorneys and former State Department aides to Clinton who had sorted her emails on their laptop computers.

Goodlatte wanted to know why the Justice Department had made side agreements promising that the FBI would destroy both Mills’ and Samuelson’s laptops after the bureau completed its search of them, making follow-up investigations impossible.

The side agreements also constrained the date range of documents that would be searched. Goodlatte asked why the time limit was necessary, since Mills and Samuelson were given immunity for any potential destruction of evidence charges.

More questions were raised by Lynch’s 30-minute meeting in her private plane with Secretary Clinton’s husband on June 27. Speaking to reporters after the incident, Lynch brushed off concerns about political interference. “My agency is involved in a matter looking at State Department policies and issues,” she said. “It’s being handled by career investigators and career agents.”

But Comey testified that the conversation on the tarmac was one reason he held a press conference a week later to declare an end to the investigation.

Feinstein is certainly right to ask why the attorney general directed the head of the FBI to use language that “tracked” with the Clinton campaign’s messaging.

More broadly, Congress has an obligation to find out if federal law enforcement agencies have acted with political bias to protect some politicians and damage others. That is an abuse of power that cannot be tolerated in a free country.

Feinstein, the ranking Democrat on the Senate Judiciary Committee, joins Republican members Ted Cruz and Lindsey Graham in asking Chairman Chuck Grassley to call on Lynch to testify. The sooner, the better.