In the early days of Anthony Clark’s campaign for Congress, the special education teacher and military veteran spent most of his free time knocking on doors in Illinois’ 7th Congressional district. Unlike most Democratic candidates who canvass in the age of data-driven everything, Clark didn't know whether the people in those houses leaned Clinton or Sanders in 2016, or even if they were Democrats or Republicans. He had no idea, in fact, whether they’d ever cast a vote in their entire lives.

That information and more—down to who put up lawn signs for which candidate in the primary—lives in VoteBuilder, a database managed by the Democratic National Committee. VoteBuilder has become the central nervous system of every Democratic campaign, housing years of information on just about every contact the party has ever made with every voter. Developed through a partnership between the DNC and a company called NGP VAN, the tool gives campaigns the inside track on potential donors, volunteers, or voters out of a pool of thousands or, in the case of a presidential election, millions of people.

But thanks to an intricate system of state-by-state rules governing who gets access to that data—a system critics say is tailor-made to protect incumbents—some Democratic primary challengers, like Clark, are being denied access to this critical pool of information by their own party.

'What’s one more way you can stack the deck against me? Deny me access to valuable information and data.' Anthony Clark, Justice Democrat Candidate

The rules and bylaws dictating access are hardly new, and several state Democratic parties allow full access to VoteBuilder for all candidates. But the 2016 election created a groundswell of energy among first-time progressive candidates, looking to challenge sitting members of Congress not only in red districts, but in blue ones they believe need shaking up. For many Democrats mounting a primary challenge, the process of merely gaining access to the party's voter data is emblematic of the entrenched system they’re running against.

“The machine protects incumbents,” says Clark, who is running against representative Danny Davis, who has held his seat for 20 years. “What’s one more way you can stack the deck against me? Deny me access to valuable information and data.”

In Illinois, the state party prevents any candidate running against an incumbent from gaining access to VoteBuilder. “We talk about growing the Democratic party, so how do you grow the Democratic party if you go after incumbents?” says Steve Brown, a spokesperson for the Illinois Democrats. “The Democratic party is creating and maintaining and enhancing a tool. Why would you want to give it to outsiders who may or may not actually be Democrats?”

Clark is running as a so-called Justice Democrat, a group that spun out of Bernie Sanders' 2016 campaign, and is challenging incumbents across the country with a progressive platform that mirrors Sanders' own. Still, the 35-year-old has been a registered Democrat since he was 18 years old. He decided to run at the urging of members of his local community, and hopes to fight back against what he views as political complacency. "They're trying to maintain power," Clark says of current members of Congress. "They're focused on a career, rather than on the people."

Rather than allow access to VoteBuilder, the state party instead directed Clark to a tool called SmartVAN, another NGP VAN product that lacks proprietary DNC voter data. While better than flying blind, as he had going door to door at the campaign's outset, SmartVAN still lacks data that could provide an edge. "Is it as effective? No," Clark says. "But we’re going to make do with what we have."

At least Illinois's rules are cut and dry. In Washington's 9th district, Sarah Smith, a Justice Democrat running a primary campaign against incumbent Democrat Adam Smith, was told that access to VoteBuilder required the endorsement of 50 percent of legislative district clubs, plus one, as well as the backing of the state party chair. But state legislators often wait until close to the actual primary to make an endorsement, Smith says, meaning her campaign would have to spend the majority of the race waiting around for endorsements before gaining access to the data. And even then, the likelihood of sitting party officials endorsing a challenger over an incumbent is low.