Speaker John Boehner’s shocking decision to resign from Congress is a sorry measure of how far right-wing extremism has immobilized the Republican Party and undermined the process of healthy government.

In abruptly quitting the arena, Mr. Boehner may have headed off the latest threat of a government shutdown. But he did so by yielding to the attack on his leadership that is being waged by some of the same Tea Party zealots and conservative naysayers who supported his ascent to speaker nearly five years ago.

Though he is deeply conservative himself, he has been tormented ever since by right-wing malcontents who have condemned any hint of the sort of political accommodation needed for legislation.

Mr. Boehner said that putting members through “prolonged leadership turmoil would do irreparable damage to the institution,” so he is yielding the gavel and quitting the House of Representatives after 25 years on Oct. 30.