Let’s start with this: House Majority Leader Eric Cantor’s defeat in Tuesday’s primary is a really big deal. Members of the House rarely lose renomination, and party leaders almost never do. At the very least, this upset shuffles the leadership team and future leadership teams. Cantor was the most likely future House speaker. Now, it will be someone else.

The first question to ask is: Why did it happen? No one knows. Not yet, at least. So be wary of anyone who claims to have a quick answer. I have no expertise when it comes to the Virginia district where Cantor and his challenger David Brat ran, or on the history of Cantor’s relationship with party actors there. The best response to the “why” question is Nate Silver’s earthquake analogy: We can understand the conditions for some rare events, even if we can’t predict the time or place.

About those conditions? Republican leaders, including whomever counts as the “establishment,” have spent more than 40 years educating rank-and-file voters that “more conservative” is always better. But they haven’t specified what “more conservative” actually means beyond attitude. So it isn’t surprising that people in the House or Senate leadership – those who are required to make and support deals with Democrats during times of divided government – will wind up accused of being squishes or RINOs. Even if we don’t know whether that is specifically the cause of Cantor’s defeat, it’s almost certainly part of the context that has made all Republican incumbents a little more vulnerable.

As for the consequences of Cantor’s loss (beyond changes in the leadership), they don’t really depend on the causes; they depend on how Republicans interpret the election.

One thing has consistently been true over the years. Whenever conservative Republican politicians are accused of not being sufficiently conservative, they react by rushing to tighten their embrace of the loudest, nuttiest, most radical, self-proclaimed conservatives. In some cases, this may be because those politicians really want to be more conservative. Other times, it may be a matter of electoral calculations, and it may even be the best strategy for most of them as individuals. Regardless, these politicians almost never fight back and defend their vision of what it means to be a real conservative or, for that matter, a real Republican.

The real surprise would be if Tuesday’s earthquake resulted in some serious attempt by mainstream conservatives to confront the radicals and the Tea Partyers. More likely, it means more extreme rhetoric, more attempts to avoid anything even hinting at compromise, more power within the party for attention-seeking talk show hosts and members of Congress willing to be entirely irresponsible and to make irresponsible choices (hopeless and pointless impeachments, government shutdowns without reasonable leverage, messing with the debt limit, and whatever they come up with next). I don’t see any substantive policy questions at issue, though, from time to time, those who consider themselves insurgents have landed on one policy or another to differentiate themselves from the rest of the party

There’s one prediction I can make for certain: It’s in the nature of elected politicians to be paranoid about re-election. A high-profile upset such as this one means that Republicans in Congress will be all the more likely to focus that paranoia on renomination contests, and not general elections. No one in the Senate has forgotten the defeats of Bob Bennett and Dick Lugar. No one in the House will forget Cantor any time soon. And given the nature of the Republican Party’s “insurgent” wing, that’s very bad news for the party, and bad news for competent government.

[Cross-posted at Bloomberg View]

Jonathan Bernstein

Jonathan Bernstein is a political scientist who writes about American politics, especially the presidency, Congress, parties, and elections.