Conservative activists caught political operatives working for House Majority Leader Eric Cantor by surprise on his own front porch on Monday evening, storming their way to victory against the GOP establishment in Virginia at a local party meeting.

Around 5:45 p.m. Monday, March 24 swaths of conservatives marched into the Henrico Board of Supervisors Meeting Room in Henrico, Virginia–inside Cantor’s congressional district. They were there for the Henrico Republican Mass Meeting, something both Cantor and his conservative primary challenger Dave Brat, an economics professor at Randolph-Macon College, had been pushing their respective supporters to attend.

The meeting, Virginia activists say, had morphed into a surprise proxy battle because of a series of recent incidents in which GOP party officials departed from tradition and excluded dozens of conservative activists from attending local party conventions. The practice has been named “slating” and has come up in other states’ GOP party chapters sought to exclude acolytes of Rep. Ron Paul.

Party officials, including top Cantor hands, were accused of slating at a March 10 meeting in Virginia Beach where 32 moderate, hand-selected Republicans were chosen for an upcoming convention instead of hundreds who had been eligible in years past.

“They ramrodded through votes to replace the list of 1000+ with a list of 32 moderates to carry the entire vote to the convention to ensure Eric Cantor’s ally State Senator Frank Wagner would be elected 2nd District chairman instead [of conservative Curtis Colgate],” said Brat campaign adviser John Pudner.

GOP State Party Chairman Pat Mullins even criticized slating in a Facebook post in late March, saying “it’s time to quit excluding and slating Republicans and time to start beating Democrats!” he wrote.

At the Henrico meeting, top Cantor aides present included his top political consultant Ray Allen, his campaign manager Marty Ryall, and Young Guns Virginia chief Michael Lowery, several people present said.

At the meeting’s outset, Don Boswell was nominated to be the mass meeting’s chairman. But when the yeas and nays were called, it became clear that conservatives defeated Boswell’s nomination. According to conservative blogger Tom White who was on site, Boswell’s nomination failed by a vote of 164-170.

Following Boswell’s defeat, conservatives nominated one of their activists, Russ Moulton, to serve as the meeting’s chairman. As the final votes were being tallied, loud cheers drowned out the count, but Moulton won by 5-10 votes, according to White.

Moulton opted to follow tradition and allow any Republican in good standing to attend the convention.

In an interview, Moulton ripped Cantor for working against conservative activists.

“I don’t understand why Eric Cantor is picking such a public fight with the conservatives in his own base,” Moulton said. “The Tea Party, the Liberty movement, pro-life conservatives, pro-gun activists. It just doesn’t make a whole lot of sense to me and I think in Henrico County and big group of them said that we weren’t going to take this anymore,” Moulton said.

“We need a unifying conservative Republican base to win elections and this divisiveness of Ray Allen, his consultant, is really, really very, very divisive, very disenfranchising, and really not helpful to them,” he added.

Brat aide Pudner called it a “stunning development gives further evidence of the surprise vulnerability of the re-election bid of the Majority Leader.”

Cantor and Brat will face-off in a June 10 primary election, and the Henrico meeting Monday has no direct impact on that race. But Pudner said it was nonetheless a sign of Cantor’s weakness with only a little more than two months before primary day.