SIOUX FALLS, S.D. — Backers of a proposed ballot measure that would cap the amount state agencies could pay for prescription drugs hope to start building support soon to put the initiative before voters in 2018, a key proponent said Wednesday.

The plan is meant to save taxpayer dollars and drive down the cost of prescriptions, supporter Rick Weiland told The Associated Press. It would impose a price limit on state drug purchases at the lowest price paid for the same drug by the U.S. Department of Veterans Affairs.

“This is going to be a very interesting campaign with Big Pharma loaded to bear because they don’t want this to become a stepping stone to other state efforts to do the same thing,” said Weiland, a former Democratic U.S. Senate candidate who is involved in several initiative campaigns.

The plan — adapted from an Ohio initiative that’s on the ballot this year — has already attracted the pharmaceutical industry’s attention. South Dakota Biotech and Washington-based Pharmaceutical Research and Manufacturers of America last week filed a court challenge to the state attorney general’s ballot question explanation.

The industry groups are asking a judge to direct Attorney General Marty Jackley to modify his explanation. The groups said in a statement that the explanation falls short because it doesn’t mention language giving supporters legal standing if the initiative is challenged in court.

Jackley said that his team works “very diligently” to ensure ballot question explanations are fair. A hearing is scheduled for Tuesday.

Weiland said the organizations missed the deadline in state law to file such a challenge, contending that the move is an attempt to tie up the initiative in court so supporters don’t have time to collect enough signatures to qualify for the ballot.

Backers must submit nearly 14,000 valid signatures to the secretary of state by November 2017 to get on the ballot in 2018. Weiland said the goal is to collect 20,000 names.

Measures have been placed on California and Ohio ballots to cap what those states pay for all prescription drugs at the lowest price the U.S. Department of Veterans Affairs pays. California’s was voted down last year after the pharmaceutical industry spent more than $100 million to oppose it. Ohio’s measure will go before voters this November.

South Dakota initiative supporters have tapped Sioux Falls City Council candidate Clara Hart to serve as chairwoman of pro-initiative group South Dakotans for Lower Drug Prices.

Hart said that pharmaceutical companies need to “wake up and learn” that people are hurting. “They need to have a heart instead of money, money all the time,” she said.