Back at the U.S. Capitol, aides to House Majority Whip Kevin McCarthy (R-Calif.) frantically huddled deep into the night. Were they plotting his next move? No one was talking.
The reactions illustrate the situation each man faces in the coming days, especially if Cantor steps down as majority leader and sparks a contentious leadership fight. Boehner, 64, is already on top and easily defeated a tea party-backed challenger a few weeks ago after insisting that he has no plans to retire. His allies, including Rep. Devin Nunes (R-Calif.) said Tuesday night that Boehner should stay on as speaker to ensure unity.
McCarthy's future is less certain. Within hours, several names emerged to challenge the 49-year old for top leadership spots. There's Rep. Cathy McMorris Rodgers (R-Wash.), currently the fourth-ranking Republican; Rep. Jeb Hensarling (R-Tex.), the head of the House Financial Services Committee; and Pete Sessions (R-Tex.), who chairs the powerful House Rules Committee and has been passed over before for leadership positions.
As Cantor hunkered down back home in Richmond, Boehner and his remaining lieutenants issued statements acknowledging the defeat. Boehner called Cantor "a good friend and a great leader." McCarthy called him "one of my closest friends." McMorris Rodgers said he was "a great friend and colleague." Their words did little to quell the concerns of rank-and-file Republicans, who were left stunned, tongue-twisted and unsure of what to do or say.
Boehner spent the evening on the top floor of Trattoria Alberto's on 8th St. near Capitol Hill. Walking along Barracks Row, any passerby might have guessed that something was up inside as two black SUVs idled on the curb.
Around 10:20 p.m., Boehner's longtime friends and frequent dining buddies, Sens. Saxby Chambliss (R-Ga.) and Richard Burr (R-N.C.), came down the steps of the restaurant in shirtsleeves but declined to comment.
"Wait for him," Chambliss said, referring to Boehner. "We're on the wrong side of the Capitol," Burr added.
A few minutes later, with the knot of his pink tie loosened deep into the chest of his white buttoned down shirt, Boehner and his security detail exited.
Reporters approached, asking if he had any response to Cantor's loss. "No," he said, twisting his face a bit. "You all know what the rules are."
A stickler for rules -- especially when engaging the press -- the "rule" Boehner referred to Tuesday night is his own personal edict that he not engage reporters in impromptu conversations if they spot him walking the halls of the Capitol.
Back at the Capitol, aides insisted that McCarthy had left the building earlier in the night, likely to sleep in his office in the Rayburn Building as he normally does. In his absence, aides could be seen conversing as cable news coverage of Cantor's defeat played on at least one television screen behind them.
Other Republicans were stunned.
Rep. Jim Bridenstine (R-Okla.) was presiding over the final house of the Tuesday session when he learned of Cantor's loss via text while in the Speaker's chair. Much earlier in the day, he was one of three junior House members that Cantor had raised money for at a Capitol Hill Starbucks during a meeting with large donors and lobbyists before the weekly House Republican Conference meeting.
"It's surprising," Bridenstine told reporters, adding that he considered Cantor a friend. He quickly turned pragmatic.
"I'm one of those guys who challenged a Republican in a primary myself and I was outspent some say 4-to-1, some say 5-to-1. This is the way the American system works and challengers sometimes have an advantage. And if you pull the right levers, anything can happen in American politics," he said.
Around a corner on the House side of the Capitol, Rep. Glen "G.T." Thompson (R-Pa.) was giving a late-night tour to constituents. He stepped away from the tour briefly to say that the unexpected loss "changes the dynamics for leadership."
When asked who might fill the void created by Cantor's loss, he said "I'm not sure who that would be at this point." Asked whether the loss might pose a challenge to Boehner's leadership, he said "I don't believe that it does."
Rep. Peter King (R-N.Y.) said he wondered whether the GOP was crumbling as a whole. “I don’t know where we go now as a party," he said in an interview. "I’m very concerned that we may go all the way to the right."
Democrats, meanwhile, were gleeful. In a notably sharp statement, House Minority Leader Nancy Pelosi (D-Calif.) called Cantor "one of the most extreme Members of Congress."
“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 midterms elections are concerned," she added, "it’s a whole new ballgame.”
The only Democrat spotted in the Capitol late Tuesday night was Rep. Joe Garcia (D-Fla.), an active participant in the months-long fight over immigration reform. Asked whether Cantor's defeat spelled the end of the immigration debate, Garcia said he isn't discouraged. He said that Cantor -- freed from the pressures of the far right of his party -- should now pursue immigration more aggressively.
"Why do you hold power if you're not doing the right thing for your country?" Garcia said. "If you're doing the right thing people tend to send you back to Congress."
Paul Kane and Robert Costa contributed to this report.