AUGUSTA – Gov. John Baldacci, acting immediately after its enactment by the Senate, vetoed a measure Thursday that would allow the Passamaquoddy Tribe to develop a racetrack casino in eastern Maine.

Concluding an expected chain of events, the House of Representatives upheld the veto right away, clearing the way for a statewide referendum on the racino proposal.

The Passamaquoddy Tribe and supporters in Washington County are promoting the racino proposal as a potential economic boon for the Down East area.

Promoters have outlined a project that could combine a harness-racing track with 1,500 slot machines, as well as a hotel, conference center, restaurants and other amenities.

Gaming opponents have challenged the racino approach to economic development, and Baldacci’s veto came as no surprise.

“My opposition to the expansion of gambling in Maine is well-documented and unwavering,” Baldacci said in a statement. “As presented, this bill would authorize doubling the total number of slot machines statewide.”

Passamaquoddy tribal Rep. Donald Soctomah of Indian Township said the issue involves a long-standing quest for prosperity in eastern Maine but was also a simple matter of fairness.

The only slot machines now in Maine are at Hollywood Slots, near the Bangor Raceway at Bass Park. A new Hollywood Slots casino with a voter-imposed limit of 1,500 slots is under construction in Bangor and is slated to open next year.

On Tuesday, the Maine House had given its final approval to the bill on a vote of 84-59.

In one sense, that appeared to demonstrate strong support. But since it was short of the two-thirds supermajority needed to override a gubernatorial veto, the House tally foreshadowed Thursday’s final result.

Enactment in the Senate on Thursday came without debate or a recorded vote and sent the measure on to the governor. Baldacci’s veto virtually bounced back, and the House, after a break to allow rank-and-file members to confer with leaders, moved swiftly to its vote to sustain Baldacci’s action.

Abandoning its earlier stance, the House vote to let the veto stand was 92-38.

“The party didn’t want to go against the governor’s veto,” said Soctomah, attributing the Democrat-controlled chamber’s support for the veto as an act of loyalty toward Baldacci in a case where the eventual outcome was clear.

“What is most troubling about this bill, however, is that it would expand gambling without the approval of Maine’s citizens,” the governor said in his veto message. “Major expansions of gaming have justifiably been brought before the people of Maine through the citizen initiative process.

“Gaming proposals like LD 805 and the one approved by the voters in November 2003 so alter the fabric of the state that all of its citizens, not just the elected members of the legislative and executive branches, deserve an opportunity to be heard,” Baldacci said.

Secretary of State Matthew Dunlap ruled in January that organizers had submitted enough valid signatures – just barely – to get their racino proposal before the Legislature.

Organizers needed at least 50,519 signatures. After rejecting close to 18,000 on various grounds, Dunlap ruled that 51,096 signatures were valid.

The question posed in the proposed legislation reads: “Do you want to allow a Maine tribe to run a harness racing track with slot machines and high-stakes beano games in Washington County?”

The referendum is expected to be scheduled for November.