ST. PAUL, Minn. — Native American tribes have emerged as key players in the legislative debates over whether states should legalize sports betting, with some opposing the idea because it could threaten their casinos and others supporting legalization but only if they retain a monopoly.

In many states, tribes are fighting sports betting or taking a go-slow approach because they worry it might force them to reopen decades-old agreements that give them exclusive rights to operate casinos and offer certain forms of gambling.

“The tribes have a major league seat at the table,” said Bill Pascrell III, a lobbyist for gambling interests that are seeking legalized sports betting across the country.

Six states have joined Nevada in allowing sports gambling since a U.S. Supreme Court ruling last year opened the door to its expansion.

In Minnesota, a bill seeking to legalize sports betting cleared its first hurdle earlier this year, passing a committee in the state Senate. But that’s likely to be as far as it goes, in large part because the state’s politically potent tribes oppose it.

Gambling “is the only successful economic development tool the tribes have ever had,” John McCarthy, executive director of the Minnesota Indian Gaming Association, told the committee.

The tribes, which operate 21 casinos and have given millions in campaign donations, are especially concerned about allowing sports betting on mobile devices, which they fear could invite wider internet gambling that could threaten their casinos.

In Texas, the only sports betting bill is almost certain to die. It was introduced by a Democrat, the minority party, in a state where casino operators from neighboring Oklahoma and Louisiana have donated millions to keep gambling out.

Two Oklahoma tribes, the Chickasaw and Choctaw nations, have given more than $5 million to Texas officeholders and candidates since 2006.

Sports betting measures introduced in Arizona and Washington state are also considered long shots, mostly because of tribal ambivalence or opposition.

In some states where tribal gambling is prevalent, sports betting bills have not been introduced at all. That’s the case in Oklahoma, as well as California and Florida, which are home to politically influential tribes that have been cool to the idea.

But elsewhere, casino-operating tribes are the ones leading the legalization efforts.

The Mohegan and Mashantucket Pequot tribes have exclusive rights to casino gambling in Connecticut and are working with the governor’s office to add sportsbooks. Two tribal casinos in New Mexico began running sportsbooks after the Supreme Court decision.

Tribal governments have contributed more than $114 million to state-level candidates and political committees over the past decade, according to an Associated Press analysis of data compiled by the National Institute on Money in Politics.