PORTLAND — As more casinos sprout up in New England, Maine officials could face the tough decision of whether to join them or keep the state casino-free.

Connecticut already has the enormous Foxwoods resort in Led- yard and is expecting to build another; Massachusetts will soon have a casino; and Rhode Island could be the next to get one.

“The domino theory is very real,” said Napolean Hill Overton, a gaming analyst with the investment firm Morgan Keegan.

“When a neighboring state enacts enabling legislation for casino entertainment, and the next-door state sees its residents’ dollars going over there, generating jobs in the next-door state and generating tax revenues to the next-door state, there’s an awfully strong urge to consider casino gaming,” he said.

Although officials in Maine still are generally opposed to large-scale gambling — the Legislature five months ago overwhelmingly denied a request by the Passamaquoddy Indians to build a casino in Calais — similar opposition has crumbled in other New England states.

Maine officials already are preparing for an expected lawsuit by the Passamaquoddy tribe, and are watching developments throughout the region.

Rhode Island Gov. Bruce Sundlun, a longtime casino opponent, last month gave up a similar battle to a Narragansett proposal to build a gaming hall south of Providence.

Although Massachusetts officials have scrapped dozens of plans for high-stakes gambling in that state, the Wampanoag tribe of Gay Head Indians is expected to build a casino in New Bedford.

The Mohegan tribe of Connecticut plans to build a gambling complex in Montville, just 10 miles from New England’s only legal casino, Foxwoods.

“So you’re surrounded by casinos, with New Hampshire as your only buffer, and they’re talking about casinos, too,” said William Thompson, a professor of public policy with the University of Nevada-Las Vegas.

“It will be a political persuader, but maybe Maine should just sort of stand back and say, `So what … maybe the best thing for Maine would be to have no casino in Maine.’ ”