Now Republicans are frothing about a newly released email message showing that the White House wanted Susan Rice, the American ambassador to the United Nations at the time, to go on television in 2012 and make the case that the attack was not a failure of administration policy. The message should have been turned over earlier because all it shows is a routine attempt to spin the news in the most favorable way to the White House. Though it is not the slightest evidence of a cover-up, it has become the foundation for the committee’s existence. Demonstrating the panel’s true purpose, Republican political operatives are already raising money by stoking donor anger on Benghazi.

Democrats who are now debating whether to participate in the committee shouldn’t hesitate to skip it. Their presence would only lend legitimacy to a farce.

Similarly, the Justice Department should not press Ms. Lerner’s contempt citation before a grand jury. She invoked her Fifth Amendment rights at a hearing last year and refused to testify, but Republicans claim, without foundation, that she waived those rights by first proclaiming her innocence. Her refusal, they said, was contemptuous of Congress. Little nuisances like constitutional rights or basic facts can’t be allowed to stand in the way when House Republicans need to whip up their party’s fury.