Boston's troubled Big Dig (search) highway project has become the intersection between investigations and political ambitions.

At least three potential candidates for governor of Massachusetts have launched investigations into the $14.6 billion construction job, which has been beset by colossal cost overruns, delays and a myriad of water leaks that have led some motorists to question the safety of the tunnels.

The probes are in addition to at least two federal investigations and a recent call by Boston's mayor for yet another review of the Big Dig's safety and finances.

"Every politician in Massachusetts has been responsible for this boondoggle, and now they are all trying to show how they are fighting to protect the taxpayers by pointing their fingers at someone else," said Boston University political analyst Tobe Berkovitz.

Massachusetts Attorney General Thomas Reilly (search), an independently elected Democrat who is eyeing a campaign next year against Republican Gov. Mitt Romney (search), has taken charge of an effort to recover as much money as possible from the contractors who worked on the project, and has also launched a civil fraud investigation into the leaks.

Outflanked by Reilly, Romney — who may also be weighing a run for president in 2008 — has ordered the state Transportation Department, which is under his control, to investigate the tunnels' safety. He is also pressing for the ouster of fellow Republican Matthew Amorello, chairman of the Massachusetts Turnpike Authority (search), the agency overseeing the Big Dig.

Romney has accused Amorello of fostering "a pattern of cover-up and stonewalling." Amorello refuses to step down.

A third potential gubernatorial candidate, Democratic Secretary of State William Galvin, has begun his own Big Dig investigation, looking into the question of whether the Turnpike has been hiding or destroying documents.

To make things even more complicated, the U.S. attorney for Massachusetts, Michael Sullivan — a Republican who has been mentioned as a possible candidate for state attorney general — has begun his own Big Dig probe.

That is at least five investigations by four potential statewide candidates.

And that's not all: The Federal Highway Administration (search) is investigating the tunnels' safety. That report is expected any day now. Next month, a congressional committee will hold a hearing in Boston on the leaks.

And Mayor Thomas Menino, up for re-election in November, sent a letter last week asking the Massachusetts Institute of Technology and Harvard Business School to look into the safety and finances of the project. MIT and Harvard have not yet responded.

The Big Dig is the most expensive highway project in U.S. history. Its cost was estimated at $2.6 billion when Congress first approved funding for it in the mid-1980s, and the project will not be finished until later this year, seven years behind schedule.

Many of the investigations date back to September, when water broke though a faulty wall panel and poured into an Interstate 93 tunnel, backing up traffic for miles. A subsequent investigation revealed hundreds of smaller leaks.

One central issue is the extent to which Bechtel/Parsons Brinckerhoff, the chief contractor, is to blame for the leaks and other problems. The firm has said it is confident an impartial review "will show the integrity of our work."

The turnpike agency has said that some issues — like the leaks — should be beyond politics. "A discussion about politics should be set to one side," said spokeswoman Mariellen Burns. "At the top rung of the ladder should be public safety."

In defense of the attorney general, Reilly spokesman Corey Welford said: "This has nothing to do with politics. Our focus is on recovering as much money as possible for taxpayers."

Jim Nuzzo, a GOP political analyst, said the politicians face a tricky task: They want to take credit for investigating the problems while dodging responsibility for them.

"It's a bit like the major in 'Casablanca' who's shocked, shocked to find there's gambling in Casablanca," Nuzzo said. "No one wants to be tarred with this."