US midterm election results: Why some US states take longer than others to count the votes

Results from Tuesday's US midterm elections are coming in at different speeds across the country, and some states may take days or longer to finish counting, because each state makes its own rules for processing, counting and reporting ballots.

In the US, states and local officials run elections. India, by contrast, has a single national body, the Election Commission of India, that conducts its general elections.

The growing use of mail-in voting is one of the main reasons for delays. Unlike a vote cast in person, a mail-in ballot has to be taken out of its envelope, and the voter's signature checked, before it can be counted.

Some states let officials start this work before Election Day. Wisconsin and Pennsylvania do not allow it to begin until polls open at 7am on Election Day.

Some states also count ballots that arrive after Election Day, provided they were postmarked by the voting deadline.

California, for instance, accepts ballots that arrive within seven days of Election Day, according to the BBC. On June 29, the US Supreme Court ruled 5-4 that federal law allows states to count such ballots, in a case over a Mississippi law. The ruling left in place laws in more than half the states and Washington, DC, that allow some late-received ballots to be counted, according to the Associated Press.

Tammy Patrick, chief programmes officer at the National Association of Election Officials, a professional body for US election administrators, told the NYT: "We want our elections to be cheap, fast and accurate, but we only get to pick two things."

Other state rules can also lengthen the count. Maine and Alaska use ranked-choice voting, in which voters rank candidates in order of preference.

Maine uses it in general elections only for federal offices, such as seats in the US Senate and House of Representatives, according to the state's secretary of state. If no candidate wins more than half the first-preference votes, the candidate in last place is eliminated and those ballots pass to each voter's next choice. The rounds continue until one candidate has a majority. Every extra round adds time, and the count could take days.

Some states also let voters fix problems with their mail ballots, such as a signature that does not match the one on file, or missing information. This process, known as curing, gives voters a chance to have their ballots counted.

In a close race, news organisations may have to wait for more ballots to be counted before projecting the likely winner. Some close contests trigger automatic recounts under state law, typically where the margin between the top two candidates falls within a range written into the law. Candidates can also challenge results in court, adding to the time needed to settle an election.

News organisations such as AP use unofficial results to project winners before all ballots have been counted. These projections differ from official results, which election authorities produce through canvassing, the checking and confirming of the count, and certification, the formal sign-off on the result, according to the BBC. The US Election Assistance Commission, a federal agency that collects election data and advises states, says results announced on election night are unofficial, even when they show 100% of precincts reporting.

California is among the states that can take longer to report results, partly because of its heavy reliance on mail-in voting. Its election officials have 30 days under state law to count ballots, review the count and certify the results, according to AP.

Alaska can also take longer. It counts mail ballots postmarked by Election Day if they arrive within 10 days, or within 15 days from overseas, according to AP.

Florida usually reports results quickly. It requires mail ballots to arrive by 7pm local time on Election Day and lets officials process them weeks in advance. State law makes it a felony to release any of those results before polls close.