An unprecedented level of lobbying money has been spent to pressure members of Congress to cheat the system by fast-tracking a vote to prevent a poor tribe in Arizona from opening a casino.

The effort to stop the Tohono O’odham tribe from building a casino in the Glendale, Arizona, area has broken lobbying contract records, putting piles of cash in the pockets of K Street dwellers for a bill that could cost the U.S. taxpayers up to $1 billion.

After failing to halt the casino through legal action, its opponents have turned to Congress—and lobbyists—for a narrowly tailored bill that would halt progress on the project.

In a time of uncertainty surrounding House Republican leadership, both proponents and opponents of the effort expect to have a vote on the bill as early as Monday.

Tohono O’odham Nation’s ownership of land near Glendale, Arizona, is rooted in tragedy. While the tribe is located west of Tucson, the federal construction of a dam and subsequent flooding ruined thousands of acres of their land, washing away homes and gravesites. This forced Congress to compensate the tribe by allowing them to buy new lands elsewhere—they chose a parcel near Glendale. The tribe wants a casino to bring in revenue to support its community.

Opponents of the Tohono O’odham Nation’s efforts say that the tribe had promised to build no additional casinos in nearby Phoenix. The Gila River Indian Community, which itself operates several casinos, has been especially adamant in its opposition. The opening of the casino could lead to “dangerous changes to the complexion of tribal gaming” elsewhere, said lead sponsor Rep. Trent Franks. But their legal challenges have been unsuccessful, which leaves the legislative route as their only option.

“The Tohono O’odham Nation dismissal of its promise to build no additional casinos in Phoenix is not something that Congress can ignore when the result will be so harmful for Indian gaming nationwide,” said Rep. Paul Gosar, a co-sponsor of the bill. “Previous Court rulings demonstrate that Congress is the only institution that can hold T.O. accountable for its fraud, misrepresentation and broken promises.”

Neither the Gila River Indian Community (PDF) nor the Tohono O’odham Nation (PDF) are wealthy. Both tribes have median household incomes of just above half the Arizona state average. But both have spent millions on lobbyists to press their causes with regard to this new casino, which is expected to open in December.

Yet in the first quarter of this year alone, the Gila River Indian Community paid lobbying firm Akin Gump $980,000, setting a record. This sum purchased the services of 22 lobbyists, who worked on this bill among other issues for the tribe. The tribe has spent at least $2.5 million each year on lobbyists since 2012 (Akin Gump notes that, following its record-breaking first quarter, the tribe’s spending on lobbying has declined—“with the successful introduction of the [casino bill] earlier this year, our activity around that matter decreased substantially,” said Akin Gump’s Don Pongrace).

The Tohono O’odham Nation, by contrast, has spent slightly more than $1 million on lobbying each year since 2012.

While it has lined the pockets of K Street lobbyists, the bill could have a far larger cost for American taxpayers. The nonpartisan Congressional Budget Office released a report predicting that, if the legislation were enacted, the Tohono O’odham would likely sue. The damages from the lawsuit could cost the taxpayer up to $1 billion if the tribe were successful.

The bill would also punish an already impoverished Indian tribe. The CBO estimate the Tohono O’odham Nation would bring in more than $100 million per year through the operation of the casino.

“This is a nation with 33,000 members, and it simply doesn’t have the financial resources it needs to provide basic governmental services,” said Tohono O’odham lawyer Heather Sibbison. “Without the legislation, we’re opening.”

The bill is scheduled for a fast-track process that would have it taken up quickly by the House of Representatives, bypassing normal rules. This is typically done for legislation with little opposition, like naming a post office.

“This precedent-making legislation has no business on the suspension calendar. As you know, suspension of the rules is for non-controversial legislation that doesn’t cost taxpayer’s money. This bill is both controversial and expensive,” wrote Rep. Raúl Grijalva in a letter to House Majority Leader Kevin McCarthy on Tuesday.

The effort’s companion bill in the Senate has already passed the body’s Committee on Indian Affairs by a voice vote, meaning that the campaign to pass the bill has legs.

Both hiring and construction for the casino are underway, said Grijalva, with an expected opening date in December.

“It is my hope that, if neighboring tribes have concerns about this development, they can work it out with the T.O,” Grijalva told The Daily Beast. “The last thing we need is Congress butting in and breaking faith with the Tribes, killing jobs, and potentially opening the federal government up to a billion-dollar lawsuit.”