- Cantor lost a primary battle in Virginia on Tuesday in a stunning upset
- The loss shakes up the Republican leadership picture in the House
- Cantor was thought to be a likely successor to House Speaker John Boehner
- NEW: Boehner reaffirms his intention to remain speaker
(CNN) -- Vanquished at the polls in a primary upset, Rep. Eric Cantor said on Wednesday that he would step down as House majority leader, triggering a scramble among conservatives to replace him.
Cantor's loss to a college professor and political novice on Tuesday in the Richmond-area campaign energized tea party supporters in a midterm year and obliterated his ambition to lead the House.
Critics and analysts said he neglected his base at home in Virginia and paid the price. Cantor called the stunning loss a "personal setback" at a news conference and appealed for party unity before announcing his decision to vacate the No. 2 job in the GOP hierarchy on July 31.
Behind closed doors, however, he addressed fellow Republicans at an emotional meeting where some colleagues were said to have cried and John Boehner reaffirmed his intention to remain speaker.
Dave Brat's upset primary victory over House Majority Leader Eric Cantor in Virginia joins a long list of political table turning at the polls. The most famous was in 1948 when Democratic President Harry Truman won the election over Republican Thomas Dewey. The Chicago Daily Tribune initially called the race for the New York governor. Click for more political upsets. 
1972: Democrat Joe Biden was a fresh faced, political newcomer when he defeated Republican incumbent Sen. Caleb Boggs. 
1976: First term Georgia Gov. Jimmy Carter bested a field of better known Democrats to become his party's presidential nominee. 
1994: Republican George Pataki, a former small town mayor and state lawmaker, beat Democratic incumbent Mario Cuomo for governor in New York. 
2004: Senate Majority Leader Tom Daschle, D-South Dakota, lost to Republican Rep. John Thune—the first time since the 1950s a party leader had lost re-election. 
2006: After losing the Democratic primary to Ned Lamont, Sen. Joe Lieberman became an Independent and won the general election. 
2010: After losing the primary to tea party backed Joe Miller, Alaska Sen. Lisa Murkowski won in the general election after mounting a write-in campaign -- the first time a senator had successfully done that in more than 50 years. 
2010: Republican Scott Brown, a Massachusetts state senator, beat Democratic Attorney General Martha Coakley in a special election for U.S. Senate. 
2014: House Majority Leader Eric Cantor lost the Republican primary to college professor Dave Brat, a political novice. Brat seen Tuesday night in Richmond, Virginia. Photos: Political upsets 
GOP 'earthquake': Cantor loses 
Chaos at Cantor headquarters after loss Boehner called Cantor, 51, a "good friend" and a "good leader" for Republicans.
5 aftershocks from Cantor's stunning upset loss
The heavily favored Cantor lost to college professor and political novice Dave Brat, who ran a spartan effort in Virginia with tea party support.
He said negative ads aired by Cantor actually wound up hurting the incumbent because it raised awareness of a race most believed the challenger had no chance to win. He characterized Cantor as more interested in leadership than in the needs of his constituents.
Turnout was low, and Cantor lost by 10 points.
"Eric Cantor lost this race as much as Dave Brat won it. He simply violated rule No. 1 of politics: go home," said CNN Chief National Correspondent John King. "This is Eric Cantor's fault. He was in Washington on primary day, not back in his district."
But Cantor disputed that analysis.
"I was in my district every week, so there's a balance between holding a leadership position and serving constituents at home but never was there a day did I not put the constituents of the 7th district of Virginia first," he said.
Opinion: Goodbye, GOP; the tea party has won
Musical chairs
The election by secret ballot for Cantor's GOP position is next Thursday, and conservatives are already demanding someone from a red state be selected to represent their views at the leadership table.
Rep. Pete Sessions of Texas told reporters he's planning to run for Cantor's post.
Current House GOP Whip Kevin McCarthy of California also is expected to do so and would be considered the frontrunner, but Rep. Cathy McMorris Rodgers of Washington state, the top woman on the leadership team, will stay put.
Cantor gave his full-throated support to McCarthy should he run. Cantor said he "would make an outstanding majority leader."
If he wins, then it would open up the No. 3 spot for someone else. So far Rep. Peter Roskam of Illinois plans to run for the whip job if it's available, but would face at least one challenger, Rep. Steve Scalise of Louisiana. More names could emerge.
Harder to get something done
GOP strategist John Feehery, formerly a top Republican congressional aide, said Cantor's defeat throws the GOP conference into chaos and will make it harder to get anything done.
The immediate fallout focused on immigration, one issue that clearly illustrates divisions between establishment Republicans and arch-conservatives.
Brat pushed the hard-line conservative position on undocumented workers in his anti-establishment campaign, slamming Cantor's support for proposals on issues around legal status.
Cantor made a final defense.
"My position on immigration has not changed. It didn't change from before the election, during the election, or the way it is today. You know, I have always said the system is broken, it needs reforms. I think it is much more desirable and frankly doable if we did it one step at a time, working towards where we have common ground and believe things in common," he said.
Brat faces another little-known college professor in the November election, Democrat Jack Trammell. The district is reliably conservative.
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CNN's Gloria Borger, Deirdre Walsh, and Dana Davidsen contributed to this report.
