The publicity was a potential boon for AfD, which has been frozen out of mainstream politics, in part, because its leaders have downplayed Nazi atrocities.

Political leaders have shunned the Alternative for Germany. But on his social media platform X, Mr. Musk is pitching the party as mainstream.

Elon Musk strongly endorsed the far-right Alternative for Germany Thursday in a discussion with the party’s leader that was broadcast live on X — a potential violation of German law.