BOONE, Iowa—Shortly after chopping up slabs of Iowa-bred pork ribs to distribute to Republicans at an event over the weekend, Wisconsin Gov. Scott Walker ticked through his Midwestern roots.

He told the crowd here that he lived in Plainfield, Iowa, then grew up in Delavan, across the state line in Wisconsin. His grandfather was a machinist in Rockford, Ill. And Mr. Walker noted that Harley-Davidsons, like the rented one that he rode to the event, are made in Milwaukee, just a few blocks from his home in Wauwatosa, Wis.

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