The voting will begin at select sites in all three counties at 11 a.m.
Polls will close at 7 p.m. Saturday.
It will then pick back up on September 3, after the holiday, and continue until September 8.
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Delaware's primary is September 10.
Polls are open from 7 a.m. until 8 p.m. and absentee ballots are also due by 8 p.m.