DENVER — There are a number of explanations circulating Tuesday night in the aftermath of House majority leader Eric Cantor’s stunning defeat in a primary to a virtually unknown Tea Party challenger and university professor, Dave Brat.

Cantor was effectively savaged by conservative media from Laura Ingraham to Erick Erickson for being too soft on immigration reform (although Democrats blame Cantor for the House’s failure to take any action on the issue, many conservatives viewed his support for a path to citizenship for DREAMers as an unforgivable sin).

After Tuesday’s shocking 11-point defeat to Brat, Cantor is being criticized for focusing more on national travel and fundraising than his suburban Virginia district and for failing to take his relatively unfunded opponent more seriously even amidst increasing signs that the effort to oust him was gaining steam.

And at least one man is attributing Cantor’s defeat to his unwillingness to defend gun rights — Dudley Brown, the executive director of the National Association for Gun Rights.

Last year, Brown’s group, the national companion organization to his Colorado-based Rocky Mountain Gun Owners, produced a video attacking Cantor for “voting with Obama” on gun control issues and, in a trademark Brown flourish, showing Cantor’s face morphing into President Obama’s.

The video references a Feb. 5, 2013 interview Cantor did with CNN’s Dana Bash less than two months after the Newtown shooting in which he indicated that he supports beefed up background checks for gun sales and even said that a system put in place in his home state of Virginia following the 2007 massacre at Virginia Tech could be a model for a nationwide measure.

“I think that we can take a lot of lessons from what Virginia did and put it in place at the federal level, because there are a lot of states that aren’t doing what Virginia is doing to try and beef up the database for the background checks to make sure that we actually can do something that does have a chance at reducing the likelihood and hopefully eliminating it from happening again,” Cantor told Bash.

A week after that interview, Brown traveled to Virginia for a press conference to unveil his video in Cantor’s district that not a single reporter attended. After just 10 people, six of whom were NAGR staffers showed up, Brown staged a photo-op with his staffers in the front row appearing to be asking questions for an email to members, according to the Virginia Gun Rights blog.

Of course, a bipartisan amendment to expand gun background checks died just two months later when it couldn’t get the 60 votes needed to break a filibuster, after intense pressure by the National Rifle Association, NAGR, which launched ads — morphing the faces of numerous Democrats and Republicans into Obama’s — in several states, and other gun rights groups.

As opposition to gun control hardened, Cantor backed away from his stance — and he retained an A rating from the NRA.

But he’s never been firm enough on gun rights for Brown.

Tuesday night after Cantor’s defeat, NAGR celebrated on its Facebook page, reminding its 3.7 million followers of its role opposing Cantor and, more recently, supporting Brat, who filled out the organization’s survey, which guarantees its support.

Last year, the National Association for Gun Rights ran Television and Radio ads in Virginia sounding the alarm that Eric Cantor was supporting key parts of Barack Obama’s anti-gun agenda.

Recently, we also told you about how Cantor voted with radical anti-gun Democrats — just last week — to spend $20 million more on Obama’s anti-gun agenda.

Cantor even refused to answer his NAGR candidate survey, but David Brat returned his Survey 100% in favor of your right to keep and bear arms!

NAGR members and supporters in Virginia have sent a loud message that voting for gun control in Congress is not acceptable.

Brat’s victory, which is already is re-writing the previous 2014 election narrative that the GOP establishment has finally figured out how to vanquish the Tea Party, is likely to scare other House Republicans into moving even an inch toward the political center for fear of losing their seat to a more conservative challenger in a primary.

And that’s exactly how Brown, who’s group’s tagline is “no compromises”, wants it.