A couple of months ago, neither Ellmers nor Cantor looked particularly vulnerable. That’s especially true in Cantor’s case, obviously. Both were attacked as supporters of “amnesty” and went up against opponents who made opposition to illegal immigration their pet issue. And both substantially outraised their opponents. Yet, when the dust cleared, the House Majority Leader lost and his less-experienced, less-entrenched colleague won.

The difference is even more stunning when one considers the margins in both races. Cantor lost by 11; Ellmers won by 18. That’s a 29-point spread. So, how to explain it? Here are a couple of reasons below:

1. A stronger opponent
Probably the biggest difference in the races. Brat turned out to be a strong candidate, proving that candidate quality can at times trump money. An economics professor, he successfully communicated to voters the detrimental impact of illegal immigration on wages for working-class Americans and the “crony corporate” culture that many GOP voters despise.
Roche, on the other hand, had an abrasive personality which was a poor fit for the people of the 2nd district. His previous interactions with Tea Party activists rubbed many of them the wrong way. Ellmers really lucked out, as Roche’s baggage prevented him from gaining traction and raising money.

2. Timing (also known as luck)
Ellmers’ primary was held May 6th, Cantor’s on June 10th. Both were attacked by opponents of immigration reform and received the support of Laura Ingraham and conservative media outlets. The difference is that in the days before Cantor’s primary, the Drudge Report had wall-to-wall coverage of the crisis on the Mexican border, casting Obama as the Pied Piper of Illegal Immigration and the Republican establishment as his fawning fans. This infuriated voters, particularly after Cantor implied he might make a deal with Obama on the issue the Friday before the primary. No crisis on the border, no illegal immigration issue in the headlines, Cantor probably wins.

3. Discontent with GOP leadership
Republican voters hate hate hate their leadership. Sometimes they hate them a little, sometimes a lot (usually after they talk about the urgent need for immigration reform). For voters in Cantor’s district, the primary offered an irresistible opportunity to give the finger to the GOP establishment. And what a finger it was. If Ellmers had been as visible as Cantor, she would have probably gone down. It used to be that incumbency was a huge advantage in holding one’s seat. Not anymore!

4. An even bigger financial advantage
Ellmers and Cantor outspent their opponents by about the same margin (around 40 to 1), yet in some ways Ellmers’ financial advantage was more decisive. That’s because Roche had a tremendous problem getting his message out there; a few weeks before the primary he had only $23,000 in the bank. It’s not necessary to outspend your opponent, you just need to spend enough money to get your voice heard. That usually means going on television, which Roche could not do.
On the other hand, Ellmers received help from pro-immigration reform groups which spent about $150,000 touting her opposition to amnesty. Brat didn’t raise much money, but he raised enough to get his message out. Roche didn’t, and that’s a big reason why he’s not in Congress. He still received 41%, though, not a humiliating loss by any means.

In the end, Ellmers won mostly because she got lucky and Cantor lost because he got unlucky. Timing was a big factor in their respective races. Had Ellmers’ race been held a month later, had Roche raised enough money, had she landed a tougher opponent, the result would probably have been different. Representative Ellmers is strongly favored to win a third term this November, but she’ll have a tougher time in the next Republican primary. In the meantime, she should run – not walk – from Mark Zuckerberg and the GOP leadership.