John Boehner, the Speaker of the US House of Representatives, has announced he will resign from Congress at the end of October. Anthony Zurcher has all the latest reaction and analysis.
Update 11:43 local time (15:43)
The man John Boehner once called a "jackass" took the stage at the Values Voter Summit just about an hour after news that the House speaker was resigning from office.
Although Republican presidential candidate Ted Cruz may have been inclined to dance on the speaker's political grave, he made reference to the surprising news only in passing.
"You want to know how much each of you terrify Washington?" Mr Cruz asked the audience of grassroots evangelical conservative at this annual conference. "Yesterday, John Boehner was Speaker of the House. Y'all come to town and somehow that changes."
"My only request," he quipped, "is, can you come more often?"
Mr Cruz has clashed repeatedly with his party's congressional leadership over the past several years, as he's advocated a more confrontational approach to negotiations with Democrats over budget matters, healthcare reform and, most recently, terminating funding for Planned Parenthood.
After his speech today, Mr Cruz expressed concern that Mr Boehner may be ending his tenure with one more effort at negotiation with Democrats.
"If it is correct that the speaker, before he resigns, has cut a deal with Nancy Pelosi to fund the Obama administration for the rest of its tenure, to fund Obamacare, to fund executive amnesty, to fund Planned Parenthood, to fund implementation of this Iran deal - and then, presumably, to land in a cushy K Street job after joining with the Democrats to implement all of President Obama's priorities, that is not the behaviour one would expect of a Republican speaker of the House," he said.
Two years ago the Texas senator broke with congressional tradition and angered his party's leadership when he led members of the House of Representatives in a backbench revolt that shut down the federal government over Obamacare funding.
When asked about Mr Cruz's presidential candidacy, Mr Boehner replied with an obscene gesture.
"If you're looking for someone to go to Washington to go along to get along - to agree with the career politicians in both parties who get in bed with the lobbyists of special interests, then I ain't your guy," Mr Cruz said during the first Republican presidential debate in August.
Now Boehner is gone, and it seems Mr Cruz's brand of high-stakes brinkmanship is gaining favour in the US capital. While the senator himself didn't take credit for the change, Oklahoma Congressman Jim Bridenstine - who introduced Cruz at the Washington event - wasn't so demur.
"We're going to get new leadership in the House of Representative," he said. "It's happening because there's a newly elected senator that showed up and started articulating principles that were consistent with the Republican platform."
He added that the Boehner-led establishment fought the Texas senator for his perceived transgressions.
It seems, however, that there's going to be a new sheriff in town.
Update: 10:45 local time (GMT 14:45)
The Establishment strikes back
While Mr Boehner may not be getting much love from the Republican party base, the former Florida governor Jeb Bush has paid tribute to the Speaker's service.
10:30 local time (GMT 14:30)
Evangelicals cheer... and a shutdown looms
When presidential candidate Marco Rubio told an audience at the Values Voter Summit here in Washington, DC, that John Boehner will resign, the crowd responded with an extended standing ovation.
The speaker was no favourite among the grassroots evangelical activists at this annual conference - and, in fact, he has become a punching bag on the campaign trail for many Republican presidential hopefuls.
Mr Boehner becomes the first casualty in this new anti-establishment wave in the Republican Party. The challenge of managing the day-to-day operations of the House of Representatives while satisfying an increasingly unruly - and growing - faction of hardcore conservative backbenchers has finally brought him down.
There once was a time when a speaker could bend the House of Representatives to his will by offering rewards and meting out punishment for transgressions. Those days are long gone, as members of Congress now answer to outside constituencies and interests.
Mr Boehner's resignation heralds a new reality in Washington - and likely means a much greater chance that this autumn's budget negotiations will end in an extended government shutdown. The Republican base has been calling for confrontation, and they're likely to get it.