The speaker of the House is the first constitutional officer mentioned in the American Constitution, well before the president. In Article 1, Section 5, the Constitution says “The House of Representatives shall chuse their Speaker.” The Speaker is thus a hugely important and prestigious figure in American life. So why would John Boehner, who wept copiously when he realized on Election Eve 2010 that he was soon to achieve this incredible honor, a lifetime dream, leave in the middle of a term and give it all up?

There is an immediate answer. Boehner has struggled since he became speaker with an unruly party caucus—a growing collection of Republican lawmakers who are, to put it gently, not interested in the pragmatic realities of policy making in a system of divided and overlapping powers. For the past five years, Boehner has tried to keep his team in check, often giving members leeway to pursue reckless tactics and radical policies, only to rein them in by turning to Democrats for votes after their efforts had turned catastrophic. But that approach was no longer working.

Trying to show that Republicans could govern responsibly, without another government shutdown or debt-ceiling showdown, he faced a nearly unprecedented motion from his own ranks to vacate the speakership, with a strong chance that he would be ousted from the post unless Democrats—at a price—bailed him out. That would have left him in a weakened and embattled state for a miserable 15 months remaining in the 114th Congress. The day after the high point of his tenure—the appearance of the Pope at his side for a joint session of Congress—he decided it was no longer worth it.

There is a bigger backstory. Since 1994, when Newt Gingrich led his party tribe from 40 years of wandering in the desert of the minority to the promised land of House majority, Republicans have become more stridently anti-government and anti-Washington. They have also, when in the majority, become less interested in trying to find policy solutions across party lines. Their desire to act like a parliamentary majority, maintaining rigid discipline and working only internally, became known as the “Hastert Rule” under Gingrich’s successor.

Perfect party discipline continued when Republicans, in the minority, faced Barack Obama in his first two years—unity that translated into reflexive opposition to everything Obama wanted to do. It was part of a broader strategy to delegitimize Obama and Democrats; to cultivate anger and unhappiness as Gingrich had done in 1994 in the midterm elections in 2010; and to seize back majority status, undo the Obama program, and cut government dramatically.

The strategy was led by a group of younger House members who called themselves the “Young Guns”—Eric Cantor, Kevin McCarthy, and Paul Ryan. They seized on the debt limit as their key issue in the campaign, promising to use it as a weapon to force Obama, and government spending, to their knees, and exploited for that purpose the populist Tea Party anger that had been triggered by the financial bailout in 2008. Aided by talk radio, conservative bloggers, and social media, they recruited radical candidates, gave them talking points, and promised immediate major cuts in spending the day they assumed the majority.

The electoral strategy worked like a charm—Republicans gained more seats in the House and in state legislatures than they had in more than 60 years, and recaptured the majority. The Young Guns had assumed that once the new lawmakers came to Washington, they could co-opt them in the interest of keeping their majority status. That was not to be. The majority that populism had wrought and House Republican leaders had exploited instead created a solid cadre of members who pushed the leaders away from realism and pragmatic compromise, abetted by the continuing drumbeat from right-wing media figures and their acolytes. Another huge election victory in 2014, which included recapturing the Senate, emboldened the radicals—the government shutdown they had pushed in 2013 did not cost them at the polls. But it left party leaders in both houses realizing that now, with Republicans controlling all of Congress, the need to show responsibility, no longer playing games with shutdowns or debt limits, was even greater. The growing strength of populist radicals resulted in the ironic primary defeat of the head Young Gun, House Majority Leader Eric Cantor, by Tea Partyite Dave Brat.

It was inevitable that these two forces—radicals flexing their muscles, demanding war against Obama from their congressional foxholes, and leaders realizing that a hard line was a fool’s errand—would collide violently.  The party outside Congress, including at the grass roots, has itself become more radical, and angrier at the party establishment for breaking promises and betraying its ideals. When polls consistently show that two-thirds of Republicans favor outsiders for their presidential nomination, it is not surprising that Ted Cruz would call his own Senate leader, Mitch McConnell, a liar on the Senate floor. Even insiders like Marco Rubio and Chris Christie have been eager to treat McConnell and Boehner like pinatas.

By any reasonable standard, John Boehner is a bedrock conservative—opposed to big government, pro-life, and in favor of big tax cuts. Boehner would have been placed at the right end of his party a couple of decades ago. But as a realist operating in the real world of divided government and separation of powers, he became a target within his own ranks. Now he is almost at the left end of a party that has gone from center-right to right-center to a place that is more radical than it is conservative—what Tom Mann and I called “an insurgent outlier.” On the verge of losing complete control, Boehner bailed. Boehner, with a month to go, may try to avert a shutdown and make the job of his likely successor, Young Gun Kevin McCarthy, easier. That won’t last long. In the new tribal world of radical politics, the first constitutional office has lost its luster.