India, Sept. 6 -- Statewide mail voting for this year's midterm elections kicked off amid a churning legal battle over President Donald Trump's attempts to limit the practice and mounting concern over Postal Service changes that some state officials blame for a rise in rejected ballots.

The developments have created a sense of uncertainty about a popular voting method used by one-third of the nation's voters.

North Carolina on Friday became the first state to widely distribute mail ballots for this year's elections, which will determine the balance of power in Congress for the remainder of Trump's term.

Election officials said that while they are closely monitoring the litigation, ballots will be mailed out as expected and the state is...