These states have unique election rules
(CNN) -- A few states in the US have slightly different rules for electing candidates.
Some states, for example, require a candidate to receive a certain percentage of the vote to get elected. If a candidate doesn't reach that threshold, the state holds a runoff election at a later date between the top two vote-getters or uses a ranked-choice system.
These rules, among other possible scenarios, mean that control of the US Senate may not be clear until months after Election Day.
In Georgia, if no local or statewide candidate receives 50% +1 vote on November 3, 2020, the top two vote-getters face off in a December 1, 2020, runoff election. If no federal candidate receives 50% +1 vote on November 3, 2020, the top two vote-getters advance to a January 5, 2021, runoff. This requirement also applies to the special Senate election, which is being run as an open election with all candidates on the same ballot, regardless of party. It does not apply to presidential races.
All candidates in Louisiana are elected by majority vote. If no candidate receives 50% +1 at the open primary/congressional primary on November 3, 2020, the top two, regardless of party, will move on to the December 5, 2020, open general/congressional general election. This threshold does not apply to presidential races.
Presidential, Senate and US House races in Maine are conducted using ranked-choice voting, which means voters can rank candidates in order of preference. If a candidate receives a majority of the first-choice votes, that person is declared the winner. But if no candidate has a majority, the ranked choice process begins.
In each round, the candidate with the fewest votes is disqualified, and the votes from the person's supporters are redistributed based on who they put as their second choice. This process continues until only two candidates remain, and the candidate with the most votes is declared the winner.
Maine is also one of two states in the nation that does not have a winner-take-all system for their Electoral College votes. That means that even if a candidate doesn't win the statewide popular vote in those states, they could pick up one or two Electoral College votes if they win in congressional districts. Nebraska is the only other state that does not have a winner-take-all system.
If no candidate for governor, lieutenant governor and treasurer receives a 50% + 1 majority on November 3, 2020, the race gets decided by the state legislature. Each state legislator and each state representative cast one vote. Democrats currently hold a decisive lead in the state legislature.
There are several scenarios in which control of the US Senate may not be known for months. Georgia and Louisiana both have Senate races that could be impacted by runoff laws. A recount could leave a seat open for months, like after the 2008 election, when Al Franken wasn't sworn in until July 2009.
Additionally, a 50-50 tie in the Senate could mean that control of the body would hinge on who the vice president is. Depending on the outcome of the presidential election, the vice president may change on Inauguration Day (January 20). If members of the new administration come from the Senate -- for example, Sen. Kamala Harris of California becoming Vice President -- it could change the chamber's makeup while replacement members are appointed or elected.
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