Transcript for House Majority Leader Defeated
We have a lot to get to. Beginning with the stunning election rocking Washington. Eric Cantor, beaten by a long-shot tea party candidate. The first house leader to lose a primary like that. ABC's Jon Karl is following the fallout. Good morning, Jon. Reporter: This is a political earthquake. Eric Cantor was widely considered to be the next speaker of the house. Now, she stands defeated, beaten by a virtually unknown tea party challenger. Thank you. Reporter: A stunned Eric Cantor, one of the most powerful republicans in Washington, and one of the most conservative, never saw it coming. Obviously, we came up short. I know there's a lot of long faces here tonight. And it's disappointing, sure. Reporter: The man who defeated a political goliath, Dave brat, a college economics professioner. Almost no one in Washington or even in Cantor's district, knew before now. We won this campaign and that's within reason. Dollars do not vote. You do. Reporter: Eric Cantor is fighting back. Reporter: Cantor spent 50 times more than brat. $5 million in slick campaign ads. While brat spent barely $100,000. Instead of ads, posting simple videos on his website. I am more conservative than Eric Cantor across the board. Reporter: The biggest issue was immigration. Brat told voters that Cantor would support president Obama on immigration reform. Cantor denied it. But at a campaign event last month, primary voters weren't believing him. I hear the inaccuracies. My family is here. I think this election is an anti-washington, anti-wall street signal to the republican party. Thives a new energy, I think, to the tea party. And what they stand for. Reporter: There will be much fallout from Cantor's defeat. But the thing that will most affect the white house, will be immigration reform. The president had hoped to get it passed in congress this year. Now, it is almost certainly dead. George, after watching Cantor go down in flames, republican leaders in congress are not going to want to touch that issue. That legislation is not going to happen right now. That's going to put more pressure on the president to act on his own, to do something about the undocumented immigrants and the deportations. Reporter: He had been holding back doing something with executive action. He didn't want to upset the possibility of passing in congress. Now, there's no reason to hold back, I'm sure. Eric Cantor was next in line to be house speaker. This will have huge implications for the house leadership for the gop and the primaries in 2016. Reporter: Yeah, it will. The first thing, this greatly increases the odds that John Boehner will continue as speaker of the house for another term. Cantor was the only person seen as a potential challenge to him. And for the 2016 election, don't look for immigration reform to be popular with those candidates. Jon Karl, thanks very much.
This transcript has been automatically generated and may not be 100% accurate.