WASHINGTON — Joining a growing list of Republicans, a former House speaker, Newt Gingrich said yesterday that Attorney General Alberto Gonzales should consider resigning. The possible presidential candidate said the botched firing of U.S. attorneys has destroyed Mr. Gonzales’s credibility as the nation’s top law enforcer.

“I think the country, in fact, would be much better served to have a new team at the Justice Department, across the board,” Mr. Gingrich said. “I cannot imagine how he is going to be effective for the rest of this administration. … They’re going to be involved in endless hearings.”

Senator Schumer, a Democrat of New York who is helping lead the investigation into the firing of eight federal prosecutors, said Mr. Gingrich’s comments pointed to building bipartisan support for a new attorney general.

“This is another important voice who believes that the attorney general should step down for the good of the country and the good of the department,” Mr. Schumer said in a statement. “We hope both the attorney general and the president heed Speaker Gingrich’s message.”

Mr. Gonzales, a former White House counsel who became attorney general in 2005, is scheduled to testify April 17 before the Senate Judiciary Committee. It is a congressional showdown believed to be a make-or-break appearance for Mr. Gonzales.