New York City could soon become the largest city in the US to give noncitizens the right to vote in local elections, a historic move that would open the ballot box to 800,000 green card holders and Dreamers.

The city council approved the measure on Thursday. Only a potential veto from mayor Bill de Blasio stands in the way of the measure becoming law, but the Democrat has said he would not veto it.

The council’s vote was a breakthrough moment for an effort that had long languished. Councilman Francisco Moya, whose family hails from Ecuador, choked up as he spoke in support of the bill.

“This is for my beautiful mother who will be able to vote for her son,” said Moya, while joining the session by video with his immigrant mother at his side.

Legally documented, voting-age noncitizens comprise nearly one in nine of the city’s 7 million voting-age inhabitants. The measure would allow noncitizens who have been lawful permanent residents of the city for at least 30 days, as well as those authorized to work in the US, including Dreamers, the children of undocumented immigrants, to help select the city’s mayor, city council members, borough presidents, comptroller and public advocate.

“It is no secret, we are making history today. Fifty years down the line when our children look back at this moment they will see a diverse coalition of advocates who came together to write a new chapter in New York City’s history by giving immigrant New Yorkers the power of the ballot,” said councilmember Ydanis Rodriguez, a main sponsor of the bill, after Thursday’s vote.

More than a dozen communities across the United States already allow noncitizens to cast ballots in local elections, including 11 towns in Maryland and two in Vermont. But New York City is the largest place by far to give voting rights to noncitizens.

Noncitizens still wouldn’t be able to vote for president or members of Congress in federal races, or in the state elections that pick the governor, judges and legislators.

The city’s move is likely to enflame an already contentious debate over voting rights. Last year, Alabama, Colorado and Florida adopted rules that would preempt any attempts to pass laws like the one in New York City. Arizona and North Dakota already had prohibitions on the books.

“The bill we’re doing today will have national repercussions,” said the council’s majority leader, Laurie Cumbo, a Democrat who opposed the bill. She expressed concern that the measure could diminish the influence of African American voters.

Noncitizens wouldn’t be allowed to vote until elections in 2023.

It’s unclear whether the bill might face legal challenges. City councilman Joseph Borelli, the Republican leader, said such a challenge is likely. Opponents say the council lacks the authority on its own to grant voting rights to noncitizens and should have first sought action by state lawmakers.