In 1988, when Michael Dukakis lose the national popular vote by more than 7 points, he won the state of Iowa by over 10 points, his second highest margin that year (ahead of his margin in Massachusetts and New York, but behind his near 12-point margin in Rhode Island). Only once since then has Iowa voted Republican, going for George W. Bush in 2004 by just over 10,000 votes (out of approximately 1.5 million cast).
The Iowa Secretary of State’s Office reported [in August that] there are now 620,584 voters registered as Republicans, compared to 598,995 Democrats.
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It’s quite a turnaround from January 2009 when Barack Obama was inaugurated and Iowa Democrats boasted a 110,000 voter registration advantage.