For the second time in four months, Senator Tom Harkin and Congressman Bruce Braley have visited a central Iowa business to highlight their support for increasing the minimum wage. Their Sunday stop in Norwalk, however, comes just days after Braley — the Iowa Democratic Party’s U.S. Senate nominee — began airing an ad attacking his Republican opponent, Joni Ernst, on the issue.

“My opponent has said that she opposes a federal minimum and that she thinks $7.25 an hour is just fine for Iowa’s minimum wage workers,” Braley said Sunday, “and that’s where she and I disagree.”

10 cents an hour and setting up “indexing” so the rate automatically goes up in the future, without the need for congressional action, “so it doesn’t become captive of a political system and that’s what’s going on right now,” Braley said Sunday.

Harkin said this “should be a voting issue” this fall.

“We’ve had a minimum wage since 1939 and it’s worked well in this country,” Harkin said Sunday. “So those who say there should be no minimum wage are really on the fringes of any kind of economic thought at all.”

Harkin and Braley toured the La Quercia company in Norwalk, a firm that makes cured meats, like its internationally acclaimed proscuito. The company’s owner has raised the starting pay for his employees to $10.10 an hour — the wage level Harkin has been pushing as a new national minimum wage. In April, Harkin and Braley visited Raygun, a Des Moines t-shirt business known for its provacative slogans to highlight the minimum wage. Raygun’s owner offers a starting pay rate of $13 an hour to his employees.