For historic data try these recommended resources
Political Data Yearbook
Great free website based on the European Journal of Political Research Political Data Yearbook includes election results, turnout levels and political party facts for over 30 nations most from the EU. Check dates updated.
Get an understanding of long term trends in voter behaviour using this social survey of the electorate which has been conducted since 1964. Reports and datasets can be downloaded.
University of Michigan. Provides free access to detailed election results at the constituency level for lower house legislative elections from over 18,000 elections from 162 nations . Some raw data is accessible.
An intergovernmental organisation which supports and promotes free fair elections. Its website provides access to a number of statistical databases. They include voter turnout
