Supporters of the Long Island Rail Road’s plan to build a third track on its Main Line in Nassau County on Wednesday celebrated news that the final obstacle to its passage — Republican nonsupport — had been resolved, clearing the way for a project they say will transform Long Island as few others in recent history.

The $2 billion project, which could begin this year after weathering a storm of public and political opposition, aims to improve the commutes of tens of thousands of LIRR riders by increasing capacity on a critical 9.8-mile stretch between Floral Park and Hicksville. The third track would also help the LIRR more quickly bounce back from service disruptions and facilitate reverse commuting, according to planners.

In addition to bringing billions of dollars to the region, the project will increase property values, including by reducing existing noise pollution and eliminating seven rail grade crossings, supporters say.

“One cannot overestimate the impact third track will have in attracting and keeping the millennial generation that will power the future Long Island,’’ said Kyle Strober, executive director of the Association for a Better Long Island, a business and planning group. ‘‘Businesses will be more likely to call Long Island home with an educated workforce and a more reliable rail system.”

The Metropolitan Transportation Authority and Gov. Andrew M. Cuomo, who resurrected the plan amid local opposition in January 2016, finally won over Sen. John Flanagan (R-East Northport) and other political holdouts in recent weeks.

“We are grateful to Senator Flanagan for acknowledging the overriding importance of this project to Long Island. It will improve the railroad’s reliability and lack of capacity, which in turn will help ensure the long-term economic health and well-being of tens of thousands of commuters,” said Denise Richardson, executive director of the General Contractors Association of New York, a construction trade group. “The time for LIRR Third Track is finally here.”

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Flanagan, Senate majority leader, pledged support for the project Wednesday, removing the likelihood of a veto from the state Capital Program Review Board’s Senate representative and clearing the way for the project to become official later this month.

Once it does, the MTA is expected to solicit bids from contractors to design and build the project on which construction is expected to begin, potentially, later this year. MTA officials have said the project will take three to four years to complete.

Despite the green light, residents along the project’s corridor remained uneasy about its impending arrival and the accompanying disruption.

“We’re in a residential area and not looking for any more noise and construction,” Holly Barbarosa, 40, of Floral Park, said Wednesday.

At the Floral Park Recreation Center — one of the epicenters for opposition to the third track, which will abut the village pool — residents’ concerns remained plentiful, despite the village leaders recently withdrawing their opposition to the plan.

“I’d be curious why they changed their minds. They obviously got something for it,” said Kevin Gormley, 44, of Floral Park, who lives near the tracks and was concerned about a potential increase in freight rail traffic.

MTA officials have promised the project will not result in changes to freight operations. But no amount of assurance was enough for some village residents.

Dave Kapell, executive director of the Right Track for Long Island Coalition — a pro-third track advocacy group — said Wednesday that while he understood the reservations still held by some residents, he was confident, in time, they would be won over as well.

“With a decision like this, you can never satisfy everybody. So it doesn’t surprise me that there are some people who don’t agree with the ultimate decision. But I think at this point they should start looking to the future,” Kapell said. “Five years from now when this project is complete, people are going to look back and say, ‘I can’t believe we lived with what we did for all that time.”

The project would bring several major benefits to the region, by adding $3 billion in personal income, $103 billion in property tax revenue and $5.6 billion to Long Island’s gross regional product 10 years after it’s built, Kapell has predicted.

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Sen. Elaine Phillips (R-Manhasset) said Wednesday that elected officials’ acknowledgment that the project is inevitable should not be seen as an abandonment of their concerns over it. Phillips said that with the project approved, her work “really begins,” as she, and other community representatives, stay on top of the MTA to make sure the agency delivers on its promises to minimize the impact of construction.

“It’s not perfect, but what’s most important is that the MTA and the Governor and the Long Island Rail Road understand that the communities have to have a voice in this process,” said Phillips, who touched on some of the political pressure put on opponents of the plan.

“This is obviously a project that the Governor strongly believes in,” Phillips said. “And he has a lot of political support around him.”

The project has also drawn wide support from businesses across Long Island, including some in the villages most affected by the construction work, which will include eliminating seven railroad grade crossings. That work will require relocating four businesses near the LIRR’s tracks.

Giuseppe Barba, manager of Umberto’s Pizzeria of New Hyde Park, said he hopes the third track brings in more commuters to the village and doesn’t worry about it hurting business.

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“Anything to bring in more people is good. I think we’ll be OK,” Barba said. “A lot of people come in from the city. If two tracks are not enough for commuters, they need a third track.”