Bernie Sanders' campaign for president is facing a serious data problem. Earlier this week, it was revealed that the campaign had accessed data belonging to Hillary Clinton's opposing campaign, made available after a security failure by a third-party vendor. The Sanders camp says the access itself was brief, no data was retained, and the staffer responsible has been fired — but the consequences have been severe. In response to the news, the campaign has been cut off from all voter data supplied by the Democratic National Committee, blocking access to a significant quantity of additional targeting work done by Sanders' own employees and volunteers.

In a press conference today, Sanders campaign manager Jeff Weaver said the DNC cutoff would put the larger efforts of the campaign on hold. "This is taking our campaign hostage," Weaver told reporters. "It’s impossible to mobilize the kind of grassroots campaign we have without access to that data." He pledged to challenge the cutoff in federal court if the matter was not promptly resolved.

"This is taking our campaign hostage."

Voter data plays a crucial role in modern campaigns, and party data provided from organs like the DNC typically serves as a starting point for those databases. Removing access to the core data also cuts off further efforts to refine voter-targeting — whether through follow-up calls or in-person canvassing. Sophisticated voter targeting was a crucial element of President Obama's 2012 campaign, built on top of similar data obtained from the central DNC.