All ballots cast during the extended early voting hours are provisional, to comply with federal law. That's because they'll have to cast provisional ballots, a process that involves extra steps. The Harris County Clerk's Office said the provisional ballots will be reviewed by its Early Voting Ballot Board. The 18th Congressional District stretches from northern Harris County to areas north, south, east and west of downtown Houston. A full list of early voting polling sites can be found on the Harris County Clerk’s elections website.