When the voter didn't emerge the evening after Halloween, Holt withdrew his Americans for Prosperity "Economic Freedom in Action" placard from the stack and draped it over the door handle.
"I've always wondered, if I knock on the door and someone isn't there," Holt said, as he ambled to the next house, "how likely are they to read it?" After Tuesday's pivotal legislative elections in Virginia, he might no longer have to just wonder.
Outside groups are pouring into these suburban neighborhoods as they try and tip the balance in the Virginia state senate, a body that can flip to Democratic control with just one seat turning from red to blue. The leading agitator: New York billionaire Michael Bloomberg, whose pro-gun control super PAC has invested $2.2 million total in northern Virginia and in one other district near Richmond -- an unprecedented sum for an election like this with no president, governor, U.S. senator or U.S. representative on the ballot.
But the bigger prize is the White House.
This "off-off-year" election in what has become a reliable purple state offers outside groups a playground to try out tools and arguments they hope can change the game in 2016. Are voters more likely to be at their door if they receive advance notice that canvassers are in the area? Are non-English speakers more likely to vote if sent mail in their native tongue? And what's the harm of not doing any grassroots engagement at all — and just winging it?
"They would like these folks to win, but on the other hand, they want to test some messages out to see what works," said Bob Holsworth, a longtime observer of Virginia politics. "It's very much what you would see at a private sector company."
The answers could determine what kind of message Hillary Clinton emphasizes, or how much time and effort a Republican candidate spends trying to win votes in the more liberal Washington suburbs.
Academics have long pined for candidates to apply the scientific method to their races, but few candidates are eager to sacrifice a possible win in order to prove intellectual points about modern campaigning.
What has changed the game is the presence of outside advocacy groups with the funding and patience to think 10 years down the road -- and aren't tied to any particular candidate or party. These groups don't need to explain to a ballroom of supporters why they lost --- they can experiment, take whatever lessons they learn, good or bad, and get back to work next time.
So at some homes in four different regions across the state, organizers like Holt won't leave any door hangers — one of four "test cells" the group has employed through Tuesday. Then during the weeks after Election Day, AFP brass will check their data set and judge whether the treatment effect was large enough to be worth producing, printing and placing the hangers in the first place, as it promotes an agenda of expanding school choice, rolling back EPA regulations and fighting the expansion of Medicaid.
In the parlance of AFP, the conservative grassroots organization at the heart of the Koch brothers' powerful network, it's running to, "test and learn."
"That took some getting used to, because my entire political career was holding a door hanger in one hand," Holt said. When testing, he has to guard his volunteers from violating the experiment's integrity: "Do you have door hangers in your car? Do you have door hangers in your mind?" he joked that he may ask his group. "I want them all."
Testing gun control messages
These tests are unfolding in an unusual campaign season that those in Virginia politics describe as suddenly dominated not by groups like AFP, but by one man: Bloomberg, whose gun safety super PAC, Everytown for Gun Safety, has flooded Virginia with advertisements that conservatives have not been able to match. Virginia is still reeling from the killings of two journalists on live television earlier this summer — and Everytown is trying to tap into that emotion.
"My daughter Alison and her cameraman were gunned down on live television. I know we can't stop all gun violence, but we can save lives if our leaders take action," Andy Parker, father of slain journalist Alison Parker, says in the ads, which then progress to attack the Republicans' gun records and backing from the NRA.
Groups like Everytown are, in a sense, running one big experiment of their own — whether they can win. But Democrats nationally have been reluctant to run on gun platforms in presidential years, especially in swing-states like Ohio or here in Virginia, where gun ownership is high and the NRA is headquartered. But that challenge is animating — even daring — to gun-control groups that are endeavoring to show Democrats like Clinton or her ally, Gov. Terry McAuliffe, that a pro-gun control message could be a political winner next year.
"You can run in the NRA's own backyard, and you're going to have support," said Colin Goddard, a survivor of the 2007 shooting at Virginia Tech who now works for Everytown.
In turn, Republicans like Hal Parrish, the Manassas mayor and state senate candidate in district 29, are looking to turn the tables on the New York-based group by casting them as outsiders in their own spots.
The other leading gun-control super PAC, former congresswoman Gabby Giffords' Americans for Responsible Solutions, is less interested than Everytown in proving a point in the South than it is in testing bolder moves to come. In a series of small targeted digital buys across the state, the group is hoping to prove whether flashy video ads or static images work better for turning out voters with high "gun violence prevention scores."
Meanwhile, women's organizations like Emily's List are trying to fine-tune their demographic targeting to see which women can be mobilized on their issue. Another liberal group, New Virginia Majority, has two main experiments embedded into its get-out-the-vote program: some new English speakers have been sent mail in their first language, while others are being asked to read it in their second.
And at the door, the civic engagement group is trying something fairly unusual in the modern are — meaningful, time-consuming conversations with voters unsure who they will vote for if they will at all, rather than the quick-touch, waste-no-time mantra of field programs of the high-tech era.
"The beauty of Virginia is that we have elections every year," explained Tram Nguyen, the group's head.
That's the thinking of groups that plan to live another day even if McAuliffe is unable to flip the chamber, a task that he has devoted tremendous political muscle toward accomplishing. Gun-control groups think that he might be able to push through firearm legislation if the Senate turns Democratic; Republicans have trained their eyes on delivering the boastful former Democratic National Committee chair a stinging defeat a year before McAuliffe is expected to try and engineer a Clinton victory in November 2016.
That's the race that is being foreshadowed Tuesday — even if Clinton or the Republicans aren't yet on the ballot.
And for data-driven groups like AFP, it's a chance to learn exactly how to win it.
"This is about as scientific as you can get," Holt said, "when dealing with people."