WASHINGTON (MarketWatch) -- In a stunning upset, House Majority Leader Eric Cantor lost a primary challenge Tuesday night to tea-party challenger David Brat, according to the Associated Press. Virginia Republican Cantor was accused by Brat, an economics professor, of backing amnesty for illegal immigrants living in the U.S. Brat is a little-known politician while Cantor is the No. 2 Republican in the House and was considered a possible successor to House Speaker John Boehner.