Couple quick notes:
Still, they'll be hard pressed to beat Linn County's run in 1994 and 1995 when some Marion voters went to the polls five times in nine weeks:
November 1994 general election: mid-term state senator Paul Pate elected secretary of state and resigns Marion-based senate seat. December: Just re-elected state rep Mary Lundby elected to senate seat. Also in December: Linn County has special election for sheriff. Also also in December: Marion and Linn-Mar school districts vote on, and reject, a merger. January: Rosemary Thomson elected to Lundby's house seat.
Thus the voters who were in the Thomson house district and the Marion or Linn-Mar school districts voted five times.
As for House 90, Dems look to have settled on Curt Hanson while the GOP is expected to run Jefferson County supervisor Stephen Burgmeier. desmoinesdem (who takes issue with my interest in Ternus speaking out on the drinking age) has a good roundup.