Well, now we know why he was so emotional yesterday. John Boehner, a devout Catholic, had wanted to see a pope address the U.S. Congress, his U.S. Congress, for 20 years. But now the pope has left Washington — and for Boehner, it would have been all downhill from there. No wonder he's resigning — not only as House speaker, but from Congress altogether.

Boehner faced, yet again, the threat of a full-scale revolt from conservatives if he refused to bring forward legislation to shut down the government in order to protest Planned Parenthood. Add to that the struggle to pay for an extension of the highway fund, the looming vote to extend the federal debt ceiling — all set against the backdrop of an angry and energized conservative base that has given Boehner no quarter, and, in fact, has come to dislike him actively, so much so that they are coalescing around presidential candidates who are running as much against the GOP leadership as they are against the Democratic president. No wonder Boehner bowed out.

This grueling struggle has been Boehner's life since he was elected speaker in 2010. The Ohio Republican is supposedly a happy warrior, but during his tenure, the only victory he’s known is victory itself: The GOP's historically massive midterm rout of Democrats in 2010, plus another big midterm victory in 2014. Boehner's GOP began this 114th Congress with control of 247 of the House's 435 seats — their largest majority in nearly 100 years. And yet: He could do nothing with his majority. The House tried to defund ObamaCare 55 times. The government shut down once. Boehner rammed through unpopular temporary funding bills three times. So many new members of his party came to power determined to challenge him, and funded by sectors of his party that did not believe (as he privately did) that comprehensive immigration reform was wise, or even that trade bills, a staple of conventional economics, were fair.

As the press waited for Boehner to announce his resignation on Friday morning, television viewers watched the pope call on world leaders to restrain their "exercise of power." Boehner, at the end, has almost none.

His collegial, old-school relationships with fellow lawmakers have kept him in office, as has his personal probity. But he was not built for a political era of intense partisanship. By the end of September, as his allies openly spoke of having to rely on Democratic votes to survive a leadership challenge, he evidently decided that he had had enough. The party he represented was not the party he governed. His resignation was a surprise, but it was not a shock.