Scott Thompson is a labor market economist and rural sociologist in Des Moines. -promoted by desmoinesdem
The large jump in registered Iowa Democrats this summer bears out anecdotal accounts from candidates and poll watchers about Republicans changing their party affiliation to vote in the Democratic primary. Statewide, Iowa had 594,199 active registered Democrats just before the June 5 primary, increasing to 618,388 by early July and holding at 618,472 in early August. In Polk County, where primary turnout was extremely high, the number of Democrats rose from 108,258 on June 1 to 114,629 in early July and ticked up to 114,812 as of August 1.
For the purposes of my work, I call this phenomenon voter fluidity. It happens when eligible voters who are already registered, with or without party affiliation, change their party status during an election cycle. Most often, a competitive caucus or primary drives that decision.