Speaker John Boehner, in a statement from his office late Tuesday night, said, "Eric Cantor and I have gone through a lot together."
"He's a good friend and 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," added Boehner, who said his thoughts Tuesday night were with Cantor, his wife Diana, and their kids.
A senior Republican leadership aide described the mood as "chaos for the leadership ranks."
"We're absolutely stunned. Honestly, we really can't believe it," said the aide, who likened it to the 2004 election defeat of Tom Daschle of South Dakota, who was Senate minority leader at the time.