PORTLAND — A federal judge has dismissed a lawsuit accusing Republican Gov. Paul LePage of using blackmail to force a charter school operator to rescind a job offer to a political opponent, a flap that roiled the Legislature and led to an impeachment effort.

U.S. District Judge George Z. Singal ruled in favor of the governor, concluding he was entitled to immunity for his actions.

An attorney for LePage’s opponent in the lawsuit, Democratic House Speaker Mark Eves, vowed to appeal within 30 days to a three-judge panel of the 1st Circuit Court of Appeals in Boston.

“We are confident that the Court of Appeals will agree that Governor LePage violated the basic rules of our Constitution when he used taxpayer money to blackmail a private organization into firing his political opponent for partisan purposes,” said Eves’ attorney David Webbert.

LePage, who had no immediate comment, has accused his political opponents of leading a “witch hunt.”

His attorney Patrick Strawbridge said the case is “without merit” and they will continue to defend against it vigorously if Eves decides to appeal.

Eves accused LePage of overstepping his authority when he used state funding as a threat to force charter school operator Good Will-Hinckley, which serves at-risk young people, into rescinding a two-year job contract. Eves’ lawsuit sought unspecified compensatory and punitive damages.

LePage’s attorneys contended that the governor acted because he felt Eves was unqualified and that the governor had immunity when it came to spending and the state budget.

Eves, who rejected claims that he was unqualified, is a trained therapist with experience with community health organizations and more than a dozen years under his belt in the field of behavioral health and family therapy.

The allegations that Eves and other critics described as part of a pattern of bullying and abuse by LePage led to an investigation by the Government Oversight Committee, which endorsed an independent report that found the acting education commissioner withheld a quarterly payment while the governor sought to influence the board of Good Will-Hinckley.

Democratic Attorney General Janet Mills concluded there was no basis for a criminal investigation into the governor’s actions.

But that didn’t stop an effort by Democrats to impeach the outspoken governor.

An impeachment order, which was viewed as a longshot, failed when the Democrat-controlled House voted to table debate indefinitely. LePage called the impeachment effort “nonsense” and “foolishness.”

Singal, in his ruling, wrote that political battles “are an inevitable and intended part of a government built on the separation of powers” and that federal courts “serve as a poor substitute mechanism for resolving such disagreements.”

Eves has said the lawsuit is necessary to ensure that state residents can exercise their rights to free speech without the fear of retaliation or revenge from the governor’s office.

Webbert, the attorney, said Eves is “determined to hold Governor LePage accountable for his abuses of power that undermine our democracy.”