That’s been one of the favorite memes of the Republican Establishment over the last couple of days. One of the big problems with an open primary system like Virginia has is that, since party registration is not required to vote for a particular party’s candidates, anyone can vote. Thus, the idea that Democrats in an Operation Chaos-type maneuver decided to vote for Dave Brat over Eric Cantor instead of voting for their own candidate has arisen.

However, there is little to no evidence to back this up. Scott Clement of the Washington Post’s blog The Fix has written a great piece on the subject. You can read it in full there (complete with helpful graphs!), but here’s the money part:

While Republican primary turnout spiked by 28 percent over 2012, according to the State Board of Elections, Cantor received nearly 8,500 fewer votes this year than he did in the 2012 Republican primary, a drop that was larger than Brat’s 7,200-vote margin of victory. Regardless of how many Democrats turned out to oppose Cantor, he still would have prevailed had he maintained the same level of support as in his 2012 landslide. If Democrats showed up in large numbers to vote against Cantor, turnout should have spiked highest from 2012 in Democratic-leaning areas, with Cantor seeing an especially large drop-off in support. In fact, turnout rose slightly more in counties that voted more heavily for Mitt Romney in the 2012 presidential election.

In my earlier post today, I looked at a couple of primary post-mortem polls from the district on the immigration issue, and the poll commissioned by Americans for a Conservative Direction is pertinent to this post as well. Robert Schlesinger of the U.S. News and World Report e-mailed Jon Lerner of Basswood Research, who actually conducted the poll, about the possibility of Democratic interference in the VA-07 Republican Primary, and he received this in response:

His response: “The party affiliation of the voters we surveyed, who voted in the Tuesday election, was 61 percent Republican, 33 percent independent, 3 percent Democrat, and the rest were something else or refused to say.” He didn’t weight the sample. He adds: There does not appear to be a meaningful level of Democratic participation in the primary. The 33 percent Independents is higher than I often see, but in states with no party registration, lots more people self-define as “Independents” while their voting behavior is clearly more strongly in favor of one party or the other.

So, while the Republican Establishment might try to tell us that Dave Brat only won because Democrats voted for him, the actual statistics don’t bear this theory out.