Ohio called off its presidential primary just hours before polls were set to open there and in three other states, an 11th-hour decision the governor said was necessary to prevent further fueling the coronavirus pandemic that has paralyzed the nation. Health Director Amy Acton declared a health emergency that would prevent the polls from opening out of fear of exposing voters and volunteer poll workers — many of them elderly — to the virus. Officials in Arizona, Florida and Illinois felt they had done enough to ensure the safety of voters, even as concerns mounted that there will not be enough poll workers in some precincts and voters will be confused after polling places in nursing homes were moved to other locations. Elsewhere, Georgia, Kentucky and Louisiana have postponed their scheduled primaries.