When Lt. Gov. Anthony Brown's gubernatorial campaign wanted to make sure that likely primary voters saw a video ad, his staff didn't rely solely on television stations to deliver the message.
They also arranged for it to run on the computer screens of individuals the campaign believes are all but certain to turn out at the polls.
And when volunteers for Attorney General Douglas Gansler's campaign walk through a neighborhood to meet with voters, they visit homes identified by computer modeling that predicts — before the doorbell is rung — how strong a supporter the person on the other side of the threshold might be.
The Democrats and Republicans running in Maryland's June 24 gubernatorial primary are embracing increasingly sophisticated digital targeting techniques that allow candidates to single out voters and aim specialized ads — as well as personal contacts — directly at them.
The practice, used extensively by the Obama and Romney campaigns in the 2012 presidential election, is a boon for candidates who want to connect with voters they might otherwise overlook.
But it has raised concerns among some privacy advocates, who point out that the practice sometimes relies on personal data — from magazine subscriptions to Internet browsing histories — that are collected with little, if any, oversight.
"Campaigns now know a lot about people just like marketing firms know a lot about people," said Eitan D. Hersh, a Yale University political scientist who has studied the method. "They want to be able to target you in every medium they're using."
The three candidates vying for the Democratic nomination — Brown, Gansler and Del. Heather Mizeur — all are using digital targeting, though not at the level practiced by the Obama campaign in 2012 or by statewide candidates in more competitive races elsewhere, such as last year's Virginia gubernatorial election.
Republican candidates, including Harford County Executive David R. Craig and Del. Ron George of Anne Arundel County, say they're also developing more sophisticated voter models and using them to place targeted ads on social media sites like Facebook, though the campaigns were more circumspect in detailing their efforts.
While campaigns have traditionally fashioned messages to appeal to broad geographic areas or demographic groups, so-called micro-targeting allows them to identify and make contact with smaller, more specific groups. Sifting through reams of data, a campaign predicts which voters are most likely to turn out to the polls — and which of those are most likely to support their candidate — and then find ways to connect with those specific people.
The method first gained prominence during President George W. Bush's re-election campaign in 2004, but advanced technology and the proliferation of data are making it easier for state and local campaigns to try.
"The art is figuring out what people's predispositions are and their likelihood of turning out," said Ken Goldstein, a political science professor at the University of San Francisco. "If you can be the micro-targeting wizard who figures out this group of people may vote — and you hit those people — you get an advantage."
The effort begins with voter registration data, which for Democrats is often delivered through a digital firm called NGP VAN. In addition to voter roll data, the product relies on other publicly available information, such as whether the voter owns his or her home or has a hunting license, to provide analysis.
Campaign consultants then add their own information such as polling data or details about consumer habits to paint a more complete picture of a voter.
When the Brown campaign unveiled its first video ad earlier this year, it used computer modeling to identify those voters who have a high probability of casting a ballot on Election Day. It then handed that list over to YouTube, which matched the names to the IP addresses that allowed for the targeting of individual computers.
So when voters identified by the campaign clicked on a clip from a late-night comedy show or a music video, they were first presented with a "pre-roll" ad from the Brown campaign.
"Micro-targeting has been around for years," said Brown campaign manager Justin Schall. "It's just that it gets better every year."
More advanced micro-targeting allows campaigns to cater the advertising itself to specific groups. A campaign, for instance, might craft an ad about gun control legislation to parents of school-age children, even if those voters aren't hard-core party members.
"You can define these parents who would likely be interested in gun safety legislation because they have school-age children and they live in the suburbs," said Martha McKenna, a Democratic political operative who works with statewide and local campaigns across the country.
"It's a more sophisticated way to figure out your voter groups when traditional methods only get you so far," she said.