The Supreme Court has set an early marker for counting post-election day ballots after the US Supreme court ruled in a 5-3 vote that Wisconsin cannot count mail-in ballots that arrive after Election Day.

Many have deemed it to be an outcome that could have significant sway on the presidential race.

It comes as Donald Trump continues rhetoric about potential voter fraud as a result of postal votes, with many fearing that it could result in a contested election between either candidate. 

However, the court rejected a Democratic attempt to allow mail-in votes, to be received up to six days after the election in Wisconsin, in a move that many see as a significant boost to Trump.

READ MORE: US Election Day 2020: When is it, how does voting work and what time will we get results?

In the ruling, Brett Kavanaugh suggested that state courts may not have the last word in interpreting state election rules.

"Under the U.S. Constitution, the state courts do not have a blank check to rewrite state election laws for federal elections" 

States that require mail-in ballots to be returned by Election Day "want to avoid the chaos and suspicions of impropriety that can ensue if thousands of absentee ballots flow in after Election Day and potentially flip the results of an election."

Republican state legislatures in some states, including Pennsylvania, have blocked efforts to speed up the counting of mail-in ballots on election night.