If you have voter registration information in your account you can segment down on that data. To segment on voter registration information go to Audience > Search.
Then choose Activity > Voter Registration. You can then choose from any of the following criteria to refine your segment: Voter Registration Type, Datetime, Organization, Location, Location Type, Voter Registration Collector, or Voter Registration Party.
After you've made your voter registration selections, click "Save Selections" and proceed with editing your segment.