That nobody saw it coming may be the biggest surprise among the many prompted by Dave Brat‘s 12-point blowout of House Majority Leader Eric Cantor. The experts didn’t see the signs because they had decided beforehand what the outcome would be and then failed to look for any contrary evidence. In other words, as is so often the case in American political commentary, the experts were blinded by a conventional wisdom of their own making.

Conventional wisdom is usually sufficient because relatively few electoral contests are “wave elections” like that of 2010, in which widespread and deep dissatisfaction with incumbents was the defining context for most voters. Thus motivated, they awarded Republicans the party’s most comprehensive election victory in 78 years, sweeping offices from one end of the ballot to the other and in every section of the country. Opposition to Obamacare and revulsion over the manner of its passage was the defining context in 2010, accompanied by a gnawing unease with the growing national debt, excessive regulation and impatience with politicians who promise one thing but do another.