The developer behind projects like Quincy's Marina Bay and Granite Links wants to build a $300 million horse racetrack and slots parlor in Wareham, a gateway to Cape Cod, in a region that hasn't yet been a part of Massachusetts' burgeoning casino industry.

To build his "racino," the developer and his Notos Group would need to convince lawmakers to pry open the 2011 casino gaming law that established three regions for so called resort casinos, with a carve-out for a slots-only location that was awarded to Plainridge Park. Encore Boston holds the greater Boston-based region A license and Springfield's MGM casino holds the western Mass. region B license.

"We think that is the right size in Wareham. It's far enough away from the existing license holders in Massachusetts so that there will be no significant destabilization...of the existing license holders," Thomas O'Connell from Notos told WGBH News.

The state's Gaming Commission never awarded a license for a resort casino in southeastern Massachusetts' region C in part because of the possibility the Wampanoag tribe would be granted federal permission to build one outside the state's control.

O'Connell has hired two of Beacon Hill's most influential lobbying firms, Considine & Furey and Preti Strategies, to pursue the project. He'll have to convince lawmakers to rewrite the law to allow a smaller slots facility for region C.

Taunton Senator Marc Pacheco, a Beacon Hill influencer, doesn't like the idea of a smaller racino in the area. Pacheco favors a full-fledged casino operation.

"We don't have to change the statute for one person or one development team. I think that would be seen as quite frankly a corrupt process," Pacheco told WGBH News Wednesday.

O'Connell says the change in law would open up competition for a smaller casino project in Southeastern Mass., not just his project. The Gaming Commission would still vet proposals before granting any license.

"We think it's an outstanding project. We think we're in the right region, in the right town, on the exact right parcel with a really, really great idea. But until the gaming commission is given the authority and the discretion to open up the entire region for a competition we'll never know," O'Connell said.