Rep. John Lewis (D-Ga.), a liberal lion and iconic veteran of the civil rights movement, is throwing his support behind Energy and Commerce Chairman John Dingell (D-Mich.) in his fight to repel a gavel challenge from Rep. Henry Waxman (D-Calif.).

Lewis’ endorsement released Thursday comes in a letter he co-signed with five other members of the Congressional Black Caucus — Reps. Jesse Jackson Jr. (Ill.), Eddie Bernice Johnson (Texas), Kendrick Meek (Fla.), Bobby Rush (Ill.) and Edolphus Towns (N.Y.) — all of whom have already announced their support for Dingell.

The Lewis endorsement is significant because of the respect the lawmaker commands in the liberal wing of the Caucus, Waxman’s base for his bid.

But CBCers have also traditionally been stalwart champions of the seniority system, which Waxman’s gambit threatens to undermine. Seniority has resulted in several of their members winning chairmanships, including Ways and Means Chairman Charlie Rangel (N.Y.) and Judiciary Chairman John Conyers (Mich.), both of whom are backing Dingell.

In their letter, the lawmakers avoided any mention of Waxman, instead stressing Dingell’s record as a legislator. “Because of his unparalleled experience as a legislative strategist and demonstrated ability to move complex legislation through the Committee and the House, we believe it is critical that the Chairman continue to serve as Chairman,” they wrote.

Dingell’s camp has been rolling out targeted lists of its supporters, while Waxman’s team has been keeping its backers private.