Maine’s Senate race is considered close, and if so, there’s an additional reason it could take longer — maybe several days — to determine who has won. The reason is that Maine now uses ranked-choice voting (RCV), and there is an independent, Green New Deal candidate, Lisa Savage, polling in the 4-5% range. If the margin between Susan Collins and her Democratic opponent, Sara Gideon is less than that when the initial count is completed, the Senate outcome would then be determined in the second round of the ranked-choice tabulating process, when Savage will be eliminated and the second-ranked choices on those ballots will be distributed either to Collins or Gideon.
The assumption is that most of Savage’s voters will rank Gideon as their second choice, since Savage is the furthest left candidate in the race. But Maine has structured that process, as I understand it, so that it won’t get to that next stage for nearly a week. I’ve been told (maybe someone has a story to link to for this) that the Secretary of State will not turn to the second round until the vote totals from every town in the state are in; since small towns take several days to finish completing that count, that means the RCV process won’t start until the slowest town has finished completing its tallies.
This delay is not at all intrinsic to RCV. That process can be completed quickly, if not for the Secretary of State’s policy choice in Maine to wait in this way.