Detail image from Maryland Live Casino’s surveillance cameras. (Courtesy of Maryland Live Casino)

PUEBLO, Colo. — The Southern Colorado Gaming and Event Center is one of a handful of tracks where residents and visitors can bet on horse and greyhound races. If voters pass a ballot measure later this year, it could become one of three locations east of the Rocky Mountains that would be allowed to expand gaming to slot machines.

That could mean hundreds of jobs for this poor exurban county, where the unemployment rate is nearly 2 points higher than the state average. To County Commissioner Sal Pace (D), that’s a considerable boost to a struggling local economy.

“It’d be a game-changer for our community,” Pace said at a recent barbeque for political elites at the Colorado State Fair, a few miles away from the racetrack. “Pueblo County needs as much economic stimulus as we can get.”

Even so, Pace isn’t sure he supports Amendment 68 just yet. In fact, the battle between supporters and opponents falls less along partisan lines than along regional and corporate lines. Neither the state Democratic nor Republican Parties have taken positions on the measure. Instead, competing casino interests are making it one of the most expensive contests of the year, not just in Colorado but in the entire country.

Coloradans for Better Schools, the committee that favors expanded gaming, has raised more than $12 million to persuade voters. The group is funded almost entirely by Mile High USA, the Rhode Island-based owners of the Arapahoe Park Racetrack, southwest of Denver, another site that would be allowed to expand gaming.

On the other side, opponents funded by  corporations like Nevada-based Ameristar Casinos and Golden Gaming and St. Louis-based Isle of Capri Casinos have raised $16 million to defeat the amendment. Those companies own casinos that already operate in three mountain towns a few hours outside of Denver; they stand to lose millions if gamblers choose more convenient gaming options closer to town.

In states across the country, battles over whether to expand or restrict gambling have become big business for campaign consultants who cash in on competing casino interests. This year, voters in seven states will weigh in on casinos in their back yards.

One of the most expensive fights will come in Massachusetts, where voters will decide whether to repeal a 2011 law authorizing casinos. Supporters of the repeal will be vastly outspent by a coalition that calls itself the Coalition to Protect Massachusetts Jobs, funded by MGM Resorts International, Mohegan Sun and Penn National Gaming.

MGM has a license to build an $800 million facility in Springfield; Penn National has the rights to add a slot parlor to its Plainridge Racecourse facility, in Plainville. And Mohegan Sun is in the running for a license to build a Boston-area casino.

California voters will decide whether to uphold or reject two gaming compacts the state has signed with the North Fork Rancheria of Mono Indians and the Wiyot Tribe, which would allow the two tribes to build a casino in Madera County, north of Fresno. The North Fork tribe would operate the casino, while the Wiyots would be given a portion of the revenue generated by the new facility.

Already, the North Fork tribe has given more than $300,000 to a committee trying to pass the measure. The Table Mountain Rancheria tribe, which operates the Table Mountain Casino in Friant, just south of Madera County, has contributed about half the $4 million raised by the committee that opposes the measure. Brigade Capital Management, a New York-based investment fund that has financial interests in another Fresno-area casino, has contributed another $1.6 million.

“Corporations are realizing that these ballot measures may have a large impact on their bottom line, or in some cases they could introduce a measure that could help their bottom line. And they are willing to spend,” said Josh Levin, vice president of programs at the left-leaning Ballot Initiative Strategy Center.

Huge spending on gambling expansion is nothing new, as Levin saw firsthand. In 2012, Levin managed an initiative in Maryland to legalize same-sex marriage. On the ballot right next to his initiative, two casino companies — MGM and Penn National — spent nearly $95 million on Question 7, which allowed a new casino to be built at a facility just south of Washington, D.C.

The two gambling interests spent more money on television in the Washington media market than President Obama, Mitt Romney and their allies combined, who were fighting over crucial votes in the Northern Virginia suburbs. Levin said the casino campaigns hired so many field workers to hand out material on Election Day that no other campaign could find their own temporary employees.

That same year, a casino company in Rhode Island spent $5 million to expand table gaming at a facility in Twin River. A Canadian company and five Native American tribes spent a combined $8.5 million fighting over casino proposals in Oregon in 2012. In 2011, two sides spent more than $7 million on initiatives in Maine that would have added slot machines at racing facilities; both measures failed.

This year, voters will weigh in on whether to allow gambling in the city of Deadwood, South Dakota. Voters in Nebraska will decide on a constitutional amendment that would allow gambling on horse racing. And in Tennessee and Kansas, measures permitting lotteries that benefit non-profits will appear on the November ballot.

With legislators reluctant to decide for or against deep-pocketed casino interests, the companies themselves are increasingly headed to the ballot box. If those companies believe a better bottom line is only a ballot initiative away, the lure becomes difficult to avoid.

“We’ve seen a trend of larger corporate participation in ballot initiatives, and I think we will continue to see that unless there are reforms to the system,” Levin said.

— Niraj Chokshi contributed to this story.