HELENA — The Montana Supreme Court on Thursday rejected an attempt by opponents of Medicaid expansion and Attorney General Tim Fox to rewrite the language of a proposed ballot initiative and void all the signed petitions that backers have gathered to date.

The justices said in a unanimous decision that delaying signature-gathering for further court proceedings would have the effect of ruling for the plaintiffs because the sponsors have only until June 20 to gather 24,175 voter signatures to place Initiative 70 on November’s ballot.

“The fiscal statement now at issue was prepared by the attorney general with the benefit of public comment, though it does not appear that petitioners availed themselves of this early comment opportunity,” the order by Chief Justice Mike McGrath said.

Initiative sponsor Kim Abbott said backers have gathered more than 2,000 signatures to date, with 50 volunteers gathering more. There is enough time left to collect the needed signatures, but the sponsors would have had to start over if the ruling had gone the other way, she said.

“In a campaign like this, you can’t retrace your steps. It’s not the nature of this kind of fieldwork. We’re glad this is behind us,” Abbott said.

Under the proposal, federal money available through the nation’s health care law would be used to expand Medicaid to people making up to 138 percent of the federal poverty level. An analysis prepared by the governor’s office estimates nearly 56,000 in the state would enroll in 2016, which would increase to up to 80,000 people by 2019.

Fox and initiative opponents had sought a court order to revise the proposal’s fiscal statement, which the attorney general’s office previously approved. They argued the statement presented a misleading account of the measure’s estimated costs by wrongly including $100 million in federal revenue unrelated to the initiative.

Gov. Steve Bullock disagreed. The initiative creates a special account for all federal funding for medical care, and the fiscal note must include it, he said in a court filing.

The justices said the differing viewpoints and the Office of Budget and Program Planning director’s decision to stand by the fiscal note means there is little chance of resolving the matter quickly.

The court declined to get involved at this point absent a clear and unmistakable error in the fiscal statement, the justices said.

The plaintiffs will have additional chances to file legal challenges if I-170 is successfully placed on the November ballot and voters approve it, the court order said.

Abbott said she expects more challenges to come.

“I think that we’re dealing with opponents that are obstructionists. They really will do anything to block health care for thousands who need it, so we expect them to challenge us all the way through,” she said.

Bullock criticized the plaintiffs’ legal challenge as an attempt to use procedural tactics to derail the effort to expand Medicaid.

“I’ve said all along that we will get this done, and today we’ve come one step closer,” Bullock said in a statement.

A spokesman for Fox did not immediately return a call for comment Thursday.

State Sen. Fred Thomas, R-Stevensville, brought the issue of the fiscal note to light last month. He said Thursday the court missed the big picture and should have reviewed the erroneous financial estimates.

“If the Supreme Court can’t sort that out in about an hour’s hearing, then they shouldn’t be on the Supreme Court,” he said.

Now, every signature gathered for the initiative will be based on false information, Thomas said.