Socialist Sen. Bernie Sanders' supporters have filed a lawsuit seeking to extend voter registration until the day of California's primary, June 7.

The federal lawsuit seeks to extend registration past Monday's deadline because of confusion about the Democratic presidential primary and how it differs from statewide primaries, the Los Angeles Times reported.

In statewide primaries, Californians can choose any candidate regardless of party, whereas the Democratic Party dictates the rules of its presidential primary. The Democrats have reportedly opened their primary to voters of no partisan preference, but not everyone may be aware.

Sanders would likely benefit from high voter turnout. It is unclear whether a judge will agree with the lawsuit's concerns about voter disenfranchisement.