In a second courtroom setback in two days for Republican leaders in North Carolina, a judge on Friday temporarily blocked a state elections board overhaul that had been condemned as a partisan diminishing of executive power.

The abolition of the existing State Board of Elections was to take effect on Sunday, less than three weeks after the Republican-controlled General Assembly approved a proposal to merge the panel with the State Ethics Commission and, ultimately, reduce the authority of Governor-elect Roy Cooper, a Democrat.

“It certainly is not going to harm the state or the agency or any agency to delay that termination for 10 days so that we can have a hearing, a more complete hearing on the legal issues, the constitutional issues,” said Judge Donald W. Stephens of Wake County Superior Court, where Mr. Cooper filed a lawsuit on Friday.

The judge, who announced his decision to grant a temporary restraining order at the end of a Friday afternoon hearing, is scheduled to hear more arguments about the disputed law on Thursday. But his ultimate role in the case, which Mr. Cooper’s lawyers say is rooted in the principle of separation of powers, will be limited: Under North Carolina law, three-judge panels hear and decide constitutional challenges to state statutes.