Majority Leader Eric Cantor decided to surrender his No 2 leadership post in the US House of Representatives after suffering a crushing primary election defeat by a little-known and underfunded economics professor from the ultra-conservative tea party wing of the Republican Party.
David Brat's double-digit and single-issue victory in Virginia - one of the most profound political upsets in recent American history - set in motion a major shake-up inside the Republican power structure, turning Mr Cantor into a lame duck until his term expires at the end of the year.
Mr Brat ran a campaign that focused on a fight against loosening immigration laws.
House Republican colleagues began jockeying for position in the coming leadership shake-up.
Representative Kevin McCarthy, who serves as the party whip and was No 3 in the House leadership, informed fellow Republicans he intended to run to succeed Mr Cantor, officials said. Representative Pete Sessions, a Texan, also signalled an interest.
Representative Steve Scalise was hoping to replace Mr McCarthy in his current spot, officials said.
Tea party candidates had not fared well in this year's primary elections to choose candidates for the November general election. Establishment Republicans had rallied to deny the tea party places on the ballot, determined to avoid a repeat of recent elections where Republicans lost safe seats in the House and Senate because insurgent tea party primary victors proved too extreme to win in the general election.
The victory was by far the biggest of the 2014 campaign season for the tea party movement, which advocates reducing the federal deficit through deep spending cuts but opposes tax increases. While largely shut out in primaries this year, tea party supporters last week forced veteran Mississippi Republican Senator Thad Cochran into a June 24 run-off with state Senator Chris McDaniel.
House Speaker John Boehner, a fellow Republican, praised Mr Cantor as "a good friend and a great leader, and someone I've come to rely upon on a daily basis" in a statement that steered clear of the immigration issue that Mr Brat put at the centre of his campaign and has divided the party for years.
Mr Cantor told downcast supporters: "Obviously we came up short."
Mr Brat and his supporters in the ranks of the tea party were triumphant.
"This is a miracle from God," Mr Brat said.
But as he looked ahead to November's elections, Mr Brat declined to spell out policy specifics.
"I'm a PhD in economics, and so you analyse every situation uniquely," he told MSNBC in an interview in which he said he preferred to keep the focus on the "celebratory issues" of the results.
The outcome probably marks the end of a political career for Mr Cantor, who had been seen as a future House speaker. His only path to keeping his seat is to run a long-shot write-in campaign in the November election.
The impact of Mr Cantor's loss on the fate of immigration legislation in the current Congress seemed clear. Conservatives will be emboldened in their opposition to legislation to create a path to citizenship for millions of immigrants living in the country illegally, and Republican leaders who are more sympathetic to such legislation will probably be less willing to try.
Many establishment Republicans say the party cannot afford to stick to an uncompromising stand on the immigration issue, given the increasing political influence of Hispanic voters, who were key in President Barack Obama's win in 2012.
Democrats seized on Mr Cantor's upset as evidence that their fight for House control this autumn is far from over.
"Eric Cantor has long been the face of House Republicans' extreme policies, debilitating dysfunction and manufactured crises. Tonight is a major victory for the tea party as they yet again pull the Republican Party further to the radical right," said the Democratic House leader, Nancy Pelosi. "As far as the midterm elections are concerned, it's a whole new ballgame."
But the big Republican margin in the House makes a Democratic takeover highly unlikely.
Mr Cantor was appointed to his first leadership position in 2002, when he became the highest-ranking Jewish Republican in Washington. It was recognition of his fundraising skills as well as his conservative voting record, at a time Republican leaders were eager to tap into Jewish donors for their campaigns. Since Mr Boehner became speaker in 2009, Mr Cantor has been seen as both a likely eventual successor and a potential rival.
Mr Brat raised just over 200,000 dollars for his campaign, while Mr Cantor spent more than one million dollars in April and May alone to try to beat back his challenge.
Mr Brat offset the cash disadvantage with endorsements from conservative activists and with help from local tea party figures angry at Mr Cantor.
In the November election, Mr Brat will face Democrat Jack Trammel, a professor at the same college, Randolph-Mason.