Why the voter file data breach by Bernie Sanders’ campaign is a big deal for Democrats

The campaign of Bernie Sanders is threatening to sue the Democratic National Committee after it cut off his access to a crucial voter database. The DNC says it made the move because some Sanders staffers had been discovered looking at private files that belonged to Hillary Clinton's campaign. The breach puts a spotlight on the outsize role such voter data files play in today’s politics.

RELATED: Bernie Sanders fights back after Democrats cut his access to voter files over data breach

What exactly is this voter file the Democrats are fighting about?

The Democratic National Committee keeps a shareable master file of all the voter information collected by campaigns across the country. The data within that file is the foundation on which every Democratic campaign builds its field organization. Campaigns use it to create more specialized lists that help them narrowly target people who might be inclined to vote for them. They are also constantly updating the master file as they reach out to voters and learn they have moved, changed their telephone numbers, etc.

If the data is supposed to be shared, what’s the problem with what the Sanders campaign did?

The campaign’s digital director and some of his team members discovered a software glitch that allowed them to access proprietary files that belonged to the Clinton campaign. These files may have revealed which particular voters Clinton is targeting and how, as well as given the Sanders campaign access to information that the Clinton campaign has gathered on the voters that was not part of the shareable file.

What is the DNC doing about it?

The DNC has temporarily cut off the Sanders campaign from accessing the database.

What does this mean for Sanders' campaign?

The move could be potentially crippling to the Sanders field operation at a time it cannot afford to slip. It desperately needs a strong showing in Iowa and New Hampshire, both of which hold nominating contests in less than two months. The Sanders campaign has warned that it will sue the DNC in federal court this afternoon if access is not immediately restored.

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Why is this data so important? Aren’t there publicly available voter registration files?

Like everything else in society, campaigns have become increasingly reliant on algorithms and apps. In this case, they help pinpoint with precision who might lean one way or another based not just on the way and frequency they have voted in the past, but also on such factors as what websites they visit, purchases they make and publications they read. The campaigns build their own voter files by adding such information to the base data they receive from the DNC. They then use it all to determine what doors to knock on, as well as who to call and email – not to mention the contents and frequency of the messages delivered to each microtargeted voter. But if a campaign is locked out of the DNC voter file, much of its digital operation becomes paralyzed.

What about voter privacy?

This breach has raised anew questions about whether the political parties are doing enough to protect the privacy of all those voters it is building unsettlingly detailed dossiers on. Digital privacy advocates warn the law is full of “carve-outs� for political campaigns when it comes to privacy. The rules that require big retailers to take steps to prevent data breaches and take other precautions to keep sensitive personal information from getting into the wrong hands often do not apply to campaigns, they say.

Did hackers get ahold of private voter information in this case?

No. The breach was limited to the Sanders campaign. The campaign did not have authorization to view the Clinton data, but the information did not spread more widely.

What about the software vendor? Isn’t it responsible for the breach?

The Sanders campaign argues it is being punished for the incompetence of NGP VAN, the political data firm that maintains the DNC voter file. The campaign said it had warned about previous breaches, and the Sanders employee who was fired for snooping on the Clinton data said he was only on that area of the site to see how exposed his own campaign’s information might be.

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