A ballot measure that would require health insurers to cover out-of-network doctor visits is dividing two sides of the medical industry in South Dakota, sparking a costly campaign and a debate over health care led by two groups with big financial stakes.

The proposal, Initiated Measure 17, would require insurance companies to allow qualified health-care professionals onto their approved list of providers, so long as the providers agree to accept the rates those insurance companies set. The measure is similar to several other states that have laws known as “Any Willing Provider” on the books.

Specialty hospitals and the South Dakota Medical Association are behind the measure. They say it will give patients wider latitude in picking their doctors.

Supporters turned in more than 30,000 signatures, a little less than twice the number required to get on the ballot. Secretary of State Jason Gant (R) certified the signatures last year.

But bigger hospitals and the insurance companies themselves oppose the measure, which they say would drive up costs. The current system, insurers say, allows insurance companies to keep costs low. Opening plans to new providers will add layers of bureaucracy that only increase patient costs.

Dozens of other states have “Any Willing Provider” rules in some form or other. Most states apply those rules only to pharmacies; others, like Utah, Wyoming, Arkansas, Idaho and Illinois, extend those rules to cover physicians, too.

Initiative backers cite a study by a University of South Dakota professor that found states with AWP laws do not have significantly higher costs than states that don’t. The professor, Michael Allgrunn, said his data suggested costs might actually go down.

Both sides are going to be well-funded enough to make their case to South Dakota voters. Supporters of the law have already spent $500,000 and started running television advertisements. Opponents haven’t begun their paid media campaigns, but insurance companies are some of the biggest spenders on political campaigns.