Eric Cantor, the Republican party's leader in the US House of Representatives, has been dethroned in one of the most stunning upsets in modern American politics.
He was beaten by a little-known Republican primary challenger backed by the "tea party" conservative movement, who rolled to victory on a wave of public anger over calls for looser immigration laws,
Cantor's loss to economics professor David Brat was the first primary setback for a leader in Congress in recent years. It may well mark the end of 51-year-old Cantor's political career.
Brat was outspent on the campaign by Cantor by more than 25 to one. Yet Cantor became widely seen in his district as focusing on national Republican politics and policy. Failing to grasp the scope of the threat, he ignored his own re-election primary race - until it was too late.
"The people are just ready for some major changes in this country," Brat said, after winning 55 per cent of the vote. "I attribute it to God. I'm a believer and so I'm humbled God gave us this win. Just an unbelievable miracle."
Cantor, bidding for nomination for an eighth term, said only: "Obviously, we came up short."
House Speaker John Boehner said Cantor was "a great leader and someone I've come to rely upon on a daily basis as we make the tough choices that come with governing".
It was unclear if Cantor intended to remain in his leadership post for the duration of the year. It was also unclear who might replace him in the new Congress if Republicans hold their majority.
Democrats seized on the upset as evidence that their fight for House control this autumn is far from over.
Democratic House leader Nancy Pelosi said: "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. As far as the midterm elections are concerned, it's a whole new ball game."
Cantor was appointed to his first leadership position in 2002, when he was named chief deputy whip of the party and became the highest-ranking Jewish Republican in Washington.
It was a recognition of his fundraising skills as well as his conservative voting record, at a time when Republican leaders were eager to tap into Jewish donors for their campaigns.
Since Boehner was appointed speaker in 2009, Cantor has been seen as both an eventual successor and at times a potential rival.
Much of the primary campaign centred on immigration, where critics on both sides of the debate have recently taken aim at Cantor. Brat accused him of being a top cheerleader for amnesty for immigrants who are living in the US illegally.
Brat teaches at Randolph-Macon College, a small liberal arts school north of Richmond. He raised just over US$200,000 for his campaign, while Cantor spent more than US$1 million in April and last month alone to try to beat back his challenge.
Additional reporting by Agence France-Presse