We study the effects of opinion polls on election results in proportional representation systems. Moderate voters have preferences over the vote shares received by the parties so that an agent’s optimal voting decision might depend on the other agents’ behavior. A voter’s information about other voters’ behavior can be improved through a series of opinion polls. We show that the mass of undecided voters decreases monotonically with the number of polls, but may not necessarily disappear. Voters who remain undecided have centrist ideologies. On average a series of polls brings the society closer to complete information even though specific polls may push the election result away from the complete information case.