Why is the vote count in the US midterm elections taking so long?

Posted ballots still arriving in some jurisdictions

An election worker checks a ballot at the Maricopa County Tabulation and Election Centre in Phoenix, Arizona. AFP

Follow the latest news on the US midterm elections 2022

Two days after the US midterm elections, dozens of races remain undecided and it is still not clear which party will control Congress.

Overseas observers may be left wondering: why is it all taking so long?

Like anything to do with elections in the US — a country where a presidential candidate can win with fewer votes than his opponent — the answer is complicated.

Patchwork of election authorities

Unlike many nations, the US does not have a centralised voting system. Instead, it is up to each state or territory to administer elections, and rules vary enormously across jurisdictions.

In Nevada, for instance, mail-in ballots are counted so long as they are postmarked by election day. Thanks to the vagaries of the postal service, that means it can take days before all eligible ballots even reach counting centres.

The Senate race in Nevada remains close and is trending towards the Republican candidate, but as of Thursday afternoon, only 83 per cent of votes had been counted and final results may not come until the weekend.

In Arizona, another critical state that will help decide who controls the Senate, hundreds of thousands of votes that were mailed in or dropped off remain uncounted.

Election officials say a large amount of early voting ballots were dropped off in the days before election day and those are still being tabulated.

Both Arizona and Nevada are also dealing with counts in their most populous counties.

Arizona's Maricopa County represents more than 60 per cent of the state's registered voters. In Nevada, workers are still counting ballots in Clark County, which represents more than 70 per cent of the state's population.

Congressional tallies

Aside form the Senate uncertainty, dozens of House of Representative races still have no winners.

News organisations often declare a winner before final vote counts are released when it is clear, based on historical voting patterns, which way the remaining ballots are likely to trend.

But this year, many races are so closely contested that it has proven impossible to call a race before the last votes are tallied.

Other delays come when there is confusion about a ballot.

Election workers may encounter issues such as signatures not matching what's on file. Fixing problems like this, known as curing a ballot, takes time.

Many US states have laws that require voters to be notified of any issues so they can be fixed before the disputed ballots are discarded.

Democratic election posters in downtown Phoenix, Arizona. The race for governor and senate are neck and neck. Willy Lowry / The National

Maricopa County Sheriff Paul Penzone speaks as election officials hold a press conference to warn against 'false election narratives' at the Maricopa County Board of Supervisors building ahead of midterm elections, in Phoenix on November 7. EPA

Democratic Senator Mark Kelly speaks at a campaign stop with Republicans who have endorsed him. Willy Lowry / The National

Senator Mark Kelly speaks with supporters ahead of a campaign event in Phoenix. Willy Lowry / The National

Maricopa County Sheriff Paul Penzone speaks at press conference on misinformation targeting the 2022 midterm election. Willy Lowry / The National

Maricopa County Board Chair Bill Gates speaks about misinformation surrounding the 2022 midterm election. Willy Lowry / The National

A man drops his ballot into drop box in Phoenix, Arizona. Willy Lowry / The National

A sign directs voters to drop box location in downtown Phoenix. Willy Lowry / The National