The Supreme Court upheld a Mississippi law that allows election officials to count mail-in ballots postmarked by Election Day, even if they are received up to five days later.

The justices decided against a lawsuit from the Republican Party, which sought to make changes for next November's midterm elections.

The decision on Mississippi not only impacts that state, since 18 states and territories in the US contemplate similar grace periods for voting by mail.

The Court's ruling was closed – 5 to 4 on the Watson v. RNC case – with the opinion written by Judge Amy Coney Barrett. The other votes in favor were from the president of the Supreme Court, John Roberts, and the justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson.

“Election laws do not establish a deadline for receipt of ballots, so they do not prevent Mississippi from counting ballots postmarked before Election Day, even if they are received later,” Justice Coney Barrett wrote.

Justice Samuel Alito wrote the dissenting opinion, in whose arguments he followed the Republican premise that this process “risks further undermining Americans' confidence in the integrity of the elections.”

Most states that have grace periods for counting votes are governed by Democrats.

The Attorney General of New York, Democrat Letitia James, welcomed the Supreme Court's decision.

"The right to vote has been a sacred promise for generations. All eligible Americans should be able to exercise that constitutional right, free from unnecessary obstacles and restrictions," he said. “Those who cast their ballots on time, in accordance with state law, should not fear that their vote will not be counted.”

This Supreme Court decision is a further defeat for Republicans, including for President Donald Trump's administration, which last week faced another negative decision to restrict voting by mail.

Why is the decision on voting by mail relevant?

The organization Voto Latino recalled that dozens of people vote by mail when they are abroad or their jobs do not allow them to do so on election day.

“Today's ruling, which reaffirms access to voting by mail, is a victory for every voter who depends on this process to participate in our elections and cast their vote on time,” the organization said. “Millions of Americans — including our military overseas, seniors, students and working families — use mail-in voting, and every one of their votes deserves to be counted.”

Voto Latino criticized President Trump's efforts and accused him of having “spread lies about voting by mail” to promote an agency considered “extremist,” impacting multicultural voters, including Latinos.

“This ruling supports confidence in our electoral process and reaffirms that the voter's voice cannot be ignored,” the organization added.