AUGUSTA, Maine — A Superior Court judge has upheld Secretary of State Matt Dunlap’s decision to reject a citizen petition that would have asked voters to allow a new casino in southern Maine.

In March, Dunlap deemed more than half the signatures on the casino petition to be invalid. Horseracing Jobs Fairness, which led the casino petition drive and spent nearly $3 million on it, appealed the decision immediately.

Judge Michaela Murphy rejected that appeal in a decision released Thursday.

“The court concludes that the procedure followed by the Secretary of State does not require the reversal or invalidation of the entire determination,” Murphy of the Justice, Business and Consumer Court wrote in the decision.

Thousands of signatures were thrown out because the signature of the notary public who signed the petition forms, Stavros Mendros, didn’t match a verified signature on file at the secretary of state’s office.

Even if the more than 18,000 signatures under dispute were revalidated by the court, wrote Murphy, the casino backers wouldn’t reach the 61,123 signature threshold required to place the question on November’s state ballot.

The plaintiffs also argued that the secretary of state’s office was overburdened with five citizen petitions in a one-month period — which together included nearly 450,000 signatures — and didn’t adequately train additional personnel who were called from other state departments to help with signature verification.

“Petitioners have not met their burden to prove that the Secretary of State’s determination was not supported by substantial evidence or that the procedure followed by the Secretary of State was so flawed as to invalidate the entire determination,” wrote Murphy.

“We are satisfied with the ruling,” Dunlap said. “We realize that those citizens who signed this petition in good faith may be disappointed, but our job is to ensure that the constitutional requirements are met, and to that end, we are gratified by the ruling.”

The casino effort is one of two citizen petitions that were invalidated by Dunlap this year and appealed through the court. The decision on the other, which would force a referendum on the legalization of recreational marijuana, is due by April 11.

Christopher Cousins has worked as a journalist in Maine for more than 15 years and covered state government for numerous media organizations before joining the Bangor Daily News in 2009.