This recent Republican primary was one where roughly 8% of the voters showed up to vote. Such low turnout meant that relatively few voters had the power to make a huge difference. On the Republican side; traditional conservative’s were outnumbered by Brats tea party supporters, followed by an unknown number of Democrats, many of who held their noses and voted for a candidate even further to the right than Cantor.
Leading to speculation that there were large numbers of Democrats crossing over and voting for Brat and swinging the election. The fact that Virginia has open primaries which allow this left that possibility open. But the broad consensus is that, no, Democrats aren't to blame or thank. They may have added to Brat's margin, but it doesn't look like they were single handedly responsible.
Like wise with the appealing narrative that he got taken down by redistricting; certainly his loss underscores the dangers of overenthusiastic gerrymandering. Virginia Republicans efforts to fix Cantor's district in 2010 did have the effect of making it far more conservative. In Eric’s case you “live by the redistricting sword, die by the redistricting sword”.
Brat’s camp might like to claim that this election was “an absolute repudiation of establishment politics” and that Eric was voted out of office because he wasn’t “sufficiently conservative” making populist claims that Eric was in bed with big business.
Brat’s claims that Eric supports "amnesty" for illegal immigrants, and was "soft" on immigration, was nothing but a coded appeal to his tea party supporter’s native prejudices.
Trite as it may seem, the more convincing explanations are based more on variations of Cantor having gone native in Washington DC … gotten too big for his britches…. lost sight of the little people back home. "Mudcat" Saunders, a well-known Democratic consultant, offered this explanation to Time:
"Was immigration an issue? Yes. Was it the deciding factor to the tune of 11%? Not no, hell no. It's a fairy tale,"
The idea of Cantor having lost touch with the voters is especially vivid when compared to the story of South Carolina Senator, Lindsey Graham, who, when faced with the same sort of skeptical constituents, restored his relationships with local GOP officials, stumped aggressively around the state, running a slew of positive TV spots focusing on what he’s done.
Cantor, on the other hand, threw a barrage of negative ads at the problem—a tactic which may have a backfired, their ham-fisted attacks only raised Brat's previously-invisible profile—while he continued to stay inside the Beltway, laying groundwork toward taking the speakership. Like spending that fateful Tuesday morning meeting with lobbyists and donors in Washington, rather than campaigning
Cantor demise has Shakespearean overtones as he became the epitome of everything that's wrong with Washington by his own actions, becoming the perfect lightning rod and the “only conduit voters had to express their anger”.