Portland residents narrowly approved a ballot question Tuesday that blocks the sale of Congress Square Plaza and gives voters more say over future attempts to sell city-owned land.

Question 1 on Portland’s ballot passed with 4,888 votes to 4,605 opposed – 51.5 percent to 48.5 percent – after a hard-fought legal and political campaign that started with city officials’ decision last year to sell part of Congress Square Plaza to the company that redeveloped the adjacent hotel.

With that sale now blocked, city officials will have to decide how to proceed and whether to seek a second citywide vote on the controversial proposal.

Turnout for the referendum was about 18 percent, less than the turnout for November’s referendum on legalizing recreational marijuana use but higher than normal for a ballot question, city officials said.

“We thought it was going to be a real squeaker and we are definitely happy with the outcome, but we have worked hard for a long time,” said David LaCasse, a leader of the Protect Portland Parks organization and a major funder of the “Yes on 1″ campaign. “Congress Square needs work but this really was, for us, about the big picture. We thought all of the parks needed better protection, which we got tonight.”

Tuesday’s vote was the latest development in a years-long fight over the future of Congress Square Plaza, a space often described as “neglected” by the city and a gathering place for the homeless. But the referendum had far broader implications than the plaza.

The approved plan adds 35 city-owned parcels to the list of 25 properties overseen by the Portland Land Bank Commission, which was established in 1999 to protect certain city-owned properties from development. Future sales of any of the 60 parcels will need support from at least eight of the nine city councilors or, if six or seven support a sale, an endorsement from a majority of city voters in a special referendum.

The vote also effectively blocks the city’s plan to sell two-thirds of Congress Square Plaza to RockBridge Capital for $523,640. The company wanted to build a one-story event center next to the Westin Portland Harborview Hotel, formerly the Eastland Park Hotel. The company also planned to provide money to renovate the remaining 4,800 square feet of the plaza.

Jim Cohen, chairman of the Forward Portland organization, which led the fight against Question 1, congratulated the initiative’s supporters who gathered at City Hall soon after the outcome became clear.

“It was a very close vote,” said Cohen, a former mayor and city councilor. “We are obviously disappointed in the results. But … the people have spoken.”

After the polls closed at 8 p.m., supporters filed into the Yes on 1 victory party at Think Tank, a co-working space only a few blocks from Congress Square. Early returns showed the “no” camp in the lead. But by 9:30 p.m., the initiative’s backers had declared victory amid cheers, hugs and high-fives.

“We hope city officials heard us loud and clear,” said Bree LaCasse, a campaign volunteer and David LaCasse’s daughter.

The issue divided voters, as Tuesday’s results showed, and heightened tensions among some of the city’s leaders.

City officials resisted the petition drive at nearly every turn, starting by refusing to give the group petition papers. Friends of Congress Square Park took the city to court and won twice, culminating with a ruling by Maine’s Supreme Judicial Court in May that required the city to hold the referendum.

City Councilor David Marshall, who opposed the sale of part of Congress Square Plaza, railed against city administrators for “unprecedented moves” to defeat the effort.

Mayor Michael Brennan and other councilors passed a pre-emptive park protection ordinance in an effort to make the issue solely about Congress Square Plaza. More recently, the city posted information about the referendum on its website that Marshall and others thought was biased toward a No on 1 vote.

“You can fight City Hall and you can win,” Marshall said Tuesday night.

The two sides reported raising close to $100,000 combined as they sought to sway voters.

The Friends of Congress Square Park helped to breathe new life into Congress Square Plaza in recent weeks by helping to recruit a food truck and putting colorful tables and a seating platform in the plaza.

The opposing campaign – led by the would-be buyer of part of the plaza, the Portland Regional Chamber and other business interests – continually sought to portray Tuesday’s vote as a referendum solely about Congress Square Plaza.

Portland resident Joe Thomas viewed the ballot question largely as a referendum on the city’s attempt to revitalize Congress Square.

“I wanted to vote ‘No’ on Question 1,” said Thomas, who works near Congress Square, as he stopped to cast his ballot at the Portland Expo. Thomas said the city’s plan to sell and redevelop the space “is going to benefit cleaning up a corner of the city that is right in the middle of the arts district.”

Erin Brown and Steve Mayer, two recent arrivals in Portland by way of Montana, said they agreed that the referendum focused on Congress Square but didn’t agree with the opposition.

“We registered today just so we could vote ‘yes’ on the park petition,” Brown said.

“It seems the City Council didn’t really do a good job of coming up with a deal for that space,” Mayer said. “This puts a clamp on selling public property.”

Pat Roche, the owner of Think Tank and a Yes on 1 supporter, said he hoped both sides could come together and put the energy of the campaign toward improving Portland’s parks, especially Congress Square Plaza.

“Now I think we’re ready as a city to take this project on with more fervor and understanding,” Roche said. “It’s so important that people don’t get caught up in the politics of this.”

Staff Writers Randy Billings and David Hench contributed to this report.