Eric Cantor will resign his post as House Majority Leader at the end of July.
The Virginia Republican was stunned in a primary loss this week and will be out of Congress at year's end.
The events have set off a leadership scramble in the House Republican caucus. Republicans will gather in a closed meeting late today to discuss how to move forward.
In the Virginia primary election, Cantor was upended by political novice and Tea Party favorite Dave Brat.
Cantor was thought to have been a logical successor to GOP House Speaker John Boehner if he stepped down in the next couple of years.