FAIRHOPE, Ala. — Four months ago, Stephen K. Bannon was plotting a takeover of Washington and the Republican Party from his office in the West Wing as chief strategist to President Trump.

On Tuesday, Mr. Bannon the private citizen stood where his latest fight had taken him: the mulch floor of a barn in southern Alabama, where he delivered a passionate plea to elect Roy S. Moore, the former judge who faces numerous accusations that he preyed on young women, some of them teenagers.

Railing against Republican leaders in Washington, the mainstream media and Mr. Moore’s many critics inside his own party, Mr. Bannon told the crowd of several hundred who had crammed into the barn: “They want to destroy Judge Moore. And you know why? They want to take away your voice.”

“If they can destroy Roy Moore, they can destroy you,” he added.

When Mr. Moore took to the stage, where an American flag the size of a billboard served as the backdrop, he worked his way through a speech that touched on everything from Common Core, to the value of military service, to bathrooms for transgender people. “They don’t want me up there. I know that,” Mr. Moore said softly, referring to his would-be colleagues in the Senate. “They don’t want somebody up there with an independent mind.”