Arizona attorney general Tom Horne has lost his battle to block an investigation into possible campaign violations.

Horne asked for a restraining order to block Maricopa County Attorney Bill Montgomery from investigating complaints that Horne used his state office for campaign activities.

Horne claimed the county attorney is biased against the attorney general because Montgomery is supporting Horne’s primary opponent. Montgomery said he is screened off from the investigation and will have no say in the probe. Horne said the investigators would be biased since they work for the county attorney.

The court called Horne’s argument “entirely unconvincing as a basis to disqualify the entire office from a mere investigation and grand jury proceeding.” Judge Mark Brain denied the request for a restraining order.

Meanwhile in another court, Horne is challenging the authority of the Arizona Clean Elections commission to also investigate alleged campaign violations against him.