Four Republicans on the Senate Judiciary Committee have sent a letter to FBI Director James Comey asking the bureau to explain the practices that led to the indictment on campaign finance charges of conservative intellectual and filmmaker Dinesh D'Souza. The lawmakers, Charles Grassley, Jeff Sessions, Mike Lee, and Ted Cruz, are apparently concerned that D'Souza might have been the victim of a selective prosecution.

"The Washington Post and other news outlets reported that the U.S. Attorney's Office said that the investigation that led to the [D'Souza] indictment began as a result of a 'routine review by the FBI of campaign filings with the FEC of various candidates after the 2012 election,'" the senators wrote. "The articles, however, did not provide any details regarding the scope and methodology of these routine reviews."

Noting speculation that D'Souza might have been singled out for scrutiny, the senators added, "To dispel this sort of public perception that Mr. D'Souza may have been targeted because of his outspoken criticisms of the president, it is important for the FBI to be transparent regarding the precise origin of this investigation." Reminding Comey that during his Senate confirmation hearings he had promised a more transparent FBI, the senators posed several questions.

First, the senators asked if the FBI does in fact conduct "regular, perhaps random review of campaign filings." Then the lawmakers asked for "all methods by which a review of campaign filings may be initiated," plus what other government agencies, such as the Federal Elections Commission, might have been involved in such reviews.

Specifically, the senators asked how and why the D'Souza review was initiated, as well as "what criteria involved in this particular review led to the suspicion that warranted further inquiry." The lawmakers also asked how many campaign filings the FBI has reviewed in the past five years, how many agents were assigned to such matters, and when the FBI began "routinely" reviewing campaign filings.

The senators made no assertion one way or the other about D'Souza's guilt or innocence in the case. But they clearly want to know if the D'Souza indictment resulted from a process that was truly random.