ST. PETERSBURG — The Tampa Bay Rowdies' quest to reach American soccer's highest rung won overwhelming approval from city voters Tuesday, giving team owner Bill Edwards the ability to transform historic Al Lang Stadium into a venue for Major League Soccer.

A jubilant Rick Baker, a former mayor widely expected to challenge incumbent Rick Kriseman, told a green-and-yellow-clad crowd that the 87 to 13 percentage-point victory was a sign the city deserves an expansion franchise.

"This was a statement from the people of St. Petersburg," Baker told about 350 people gathered at Al Lang Stadium. "We know we have the coolest downtown in the Southeast. We want to widen that gap."

It was a statement made by less than 20 percent of eligible voters. Just over 28,000 votes were cast, nearly 90 percent by mail.

Still, said Kriseman, who shared the stage with his probable rival, the numbers don't lie.

"When you see a margin like this?" he said. "It's tough to beat that."

The referendum will allow city officials to begin negotiating a 25-year lease with Edwards, who wants to spend up to $80 million to expand the stadium's capacity to 18,000 seats.

Despite the landslide vote, nothing will happen unless MLS decides to grant one of four expansion teams to St. Petersburg. A dozen cities are vying for those franchises over the next two years, including Phoenix, San Diego and Nashville.

In unofficial results with all 93 precincts reporting, voters approved the referendum by 24,750 votes to 3,651 votes as of 8 p.m. Tuesday.

The vote marked a departure from past fights to alter the city's waterfront. Nearly a decade ago, opposition squashed plans to build a new ballpark for the Tampa Bay Rays at Al Lang — the same venue that now hosts the Rowdies.

Similar battles defeated plans to turn Albert Whitted Airport into parkland in 2003 and to replace the St. Petersburg Pier with the Lens in 2013.

Edwards did not attend Tuesday's rally. The day before the vote, he announced he would be taking a brief medical leave to have a pacemaker installed.

He hasn't been much of a visible presence on the campaign trail. Instead, Baker has been the public face of the Rowdies' effort, presenting the idea to City Council, which unanimously authorized the referendum in March, and to the city's many neighborhood associations.

Baker's visible role with the Rowdies could signal his return to public life. It has long been speculated that the former mayor will run against Kriseman this fall. Kriseman supports the Rowdies' MLS bid but hasn't actively stumped for it.

No organized opposition emerged, in part because the proposed plan wouldn't expand the footprint of the stadium. The team pledged that a seating deck wouldn't be any higher than the neighboring Mahaffey Theater and that LED lighting would be used to minimize glare. What's more, a recent city parking study determined ample parking existed for game days.

Perhaps the biggest carrot was Edwards' promise that he would pay all of the costs of the upgrade himself. No city, state or federal money would be involved, he said. Edwards even paid the $271,000 price tag to hold Tuesday's special election.

Still, some activists have voiced concerns that an ongoing federal lawsuit, which alleges Edwards drained a mortgage company, could imperil his ability to pay the league's $150 million franchise fee and millions in upgrades.

The City Council will need to approve an ordinance before negotiations between the city and the team could begin. The two sides could reach an agreement before the city gets an expansion team, but it wouldn't go into effect unless MLS decides to expand to the city.

The city's eight council members would have to approve any final deal with a super majority of six votes.

Despite the uncertainty, fans were excited Tuesday.

Ron Knaus, 79, said a having an MLS team play on the city's waterfront would be a boost for the Sunshine City.

"They'll see all that water and it will make an impact on audiences outside the Tampa Bay area," Knaus said. "Anytime we can advertise our waterfront community, I'm all for that."

Contact Charlie Frago at cfrago@tampabay.com or (727)893-8459. Follow @CharlieFrago.