With a price tag of $1.2 billion at completion, the rail line is expected to serve just 2,150 commuters a day when it starts operating in three years. It will not link to the Orlando airport or Disney World, among the region?s biggest traffic generators. Florida?s governor is even considering killing the project, worried that local government officials will rebel if they have to cover any shortfalls at the fare box.

But the so-called SunRail project has survived, at least so far, a testament to the ability of one congressman to help push through hundreds of millions of dollars in federal spending, even at a time of deep concern over ballooning federal deficits.

Representative John L. Mica, a Florida Republican and chairman of the House Transportation and Infrastructure Committee, has spent years badgering federal agencies, bullying state officials, blocking Amtrak naysayers and trying to bypass federal restrictions to build support and squash opposition to the commuter line.

While Congress is often stalled or bitterly divided in dealing with some of the biggest issues facing the nation, its members are often remarkably successful in promoting industries or more parochial concerns. Mr. Mica?s championing of the SunRail project has won praise among many officials and business leaders here, who say it is vital to the future of the traffic-clogged region.

But skeptics question whether Mr. Mica?s real goal is to give a taxpayer-financed gift to CSX, the freight rail giant and a generous Mica campaign donor, which would get $432 million for its tracks and for upgrades to tracks it owns elsewhere in the state. Other Florida businesses close to Mr. Mica also stand to benefit if the project is built.

?His dedication to SunRail is not for mass transit ? it is for helping CSX to get government funds for its private freight lines,? said State Senator Paula Dockery, a Republican and a chief critic of the project.

The congressman is unapologetic about SunRail. ?Everybody has different vested interests,? Mr. Mica said in an interview. ?But you look at what is being proposed on paper, and it just make sense.?

Mr. Mica first proposed the commuter system in 1992 after he won his first race for the House after a career that included stints as a real estate developer, a lobbyist and chief of staff to Senator Paula Hawkins, Republican of Florida. The CSX track, which for decades has also been used by Amtrak, already connects a string of communities north and south of Orlando. Commuter rail, Mr. Mica argued, could carry many more passengers and be far less costly than adding a single lane to an Interstate highway.

?For as long as I have been in Congress, Central Florida has been sending its mass transit money to New York, Philadelphia, Chicago and now to other cities ? that is where our gas tax dollars have gone,? he said.

But getting even a small fraction of the 2.3 million people living along the rail corridor to ride trains may be difficult, state officials acknowledge. Separating drivers from their cars would be like forcing Mickey and Minnie Mouse to divorce.

The federal government, wary of financing boondoggle projects, has strict rules on how ridership projections are calculated. Florida?s Department of Transportation, mindful of Mr. Mica?s keen interest, looked for ways to push up the number of projected riders, efforts that federal regulators found dubious.

Florida officials, for example, assumed that large numbers of commuters heading from one point in the suburbs to another would be willing to undertake a bus-to-rail-to-bus trip, a travel pattern that federal officials told them ?cannot be found on any existing commuter rail service in the United States.?

Mr. Mica describes himself as a fiscal conservative, arguing that ?all taxpayer-funded infrastructure projects must be wise investments.? But he has pulled strings in Washington to get special consideration for the project.

Kitty Bennett contributed research.