Minnehaha County commissioners Tuesday postponed deciding where residents will be allowed to vote in next year’s elections after expressing doubts about the effectiveness of electronic poll books. The Sioux Falls School District was first in the state to experiment with e-poll books and voting centers in 2011 with Secretary of State Jason Gant’s encouragement. Since then, several other local governments have used the system, which enables residents to vote at any of several voting sites throughout the jurisdiction. The electronic poll books ensure people don’t vote more than once. One problem the school district had was getting enough ballots to each voting center. Because any voter can go to any polling place to vote, each site must stock ballots that contain every combination of races that day.