When Apple unveils a new product, its most loyal and eager customers frequently line up outside of its stores in the hopes that they’ll be one of the first to get their hands on it.

But as important as the Apple Store is to Apple, when it comes to the iPhone, Best Buy is an increasingly important partner.

That’s because a report by research firm  Consumer Intelligence Research Partners (CIRP) shows that Best Buy is today selling nearly as many iPhones as Apple itself is. As detailed by AllThingsDigital’s John Paczkowski:

According to CIRP’s data, Apple sold 15 percent of all iPhones purchased in the U.S. during the period of the survey (retail, 11 percent; online, 4 percent). Meanwhile, AT&T sold 32 percent via its online and retail stores; Verizon, 30 percent — again, online and off — and Sprint, 7 percent.

And Best Buy? The big-box retailer sold 13 percent, just 2 percent shy of Apple itself. The remaining 3 percent is “Other,” which I’m told is a combination of retailers like Radio Shack and Walmart and respondents who received their iPhone as a gift and didn’t know where it was originally purchased.

As CIRP told Paczkowski, the Apple Store may figure prominently in the Apple retail strategy, and be a crucial part of the Apple brand, but “there are four times as many Best Buy stores, and probably 20 times as many AT&T, Verizon, and Sprint stores, so aggressive distribution through all these channels is critical to Apple’s US strategy.”

The fact that so many iPhones are being sold through Best Buy is obviously a boon to the consumer electronics retailer, which has struggled in recent years. It’s also a sign that the iPhone has truly become a mainstream device. When it was first launched, the iPhone’s primary customer was the ‘early adopter’ type with cash to spend on high-end devices, but now you’ll see the handsets everywhere you go.

Whether the mainstreaming of the iPhone will eventually catch up with Apple and give competitors opportunity to reach tech-savvy, free-spending consumers looking to be different remains to be seen. In the meantime, you can be sure Apple and Best Buy are enjoying the fruits of their retail relationship.