Early voting in Maryland begins on Oct. 27 and continues through Nov. 3, and election day is Nov. 8.
Democrat David Trone and Republican Neil Parrott are competing for District 6's congressional seat.
Candidates squared off Wednesday in their only debate ahead of November's general election.
Election officials can begin counting ballots on Oct. 1.
The plan will not impact Baltimore, which uses the 410 and 443 area codes.
The general election could take until December or early January to be certified if mail-in ballots are counted after Election Day.
More than half of Maryland residents support the legalization of cannabis, according to a March 2022 Goucher College poll.
At the opening event, multiple state and federal Democratic nominees and elected officials encouraged voters to canvass for Democratic nominee Wes Moore.
He will face Republican Dan Cox in November’s general election.