Ernst, 43, a state senator, is one of five Republican candidates in the June primary. U.S. Rep. Bruce Braley is the only Democrat in the race and is believed to have a good chance of winning the seat now held by Tom Harkin, a Democrat retiring after 40 years in the House and Senate.
Like her rivals, Ernst needs a way to distinguish herself in the crowded field -- and appears to believe her farm background will do the trick. In the commercial, titled "Squeal," she says her parents "taught us to live within our means" and she would like to pass the message to Washington.
"I grew up castrating hogs on an Iowa farm. So when I get to Washington, I'll know how to cut pork,"she says in the commercial. "Washington's full of big spenders. Let's make 'em squeal."
The commercial began airing this week on cable TV in Des Moines.
Mark Jacobs, a former utility executive in Texas, was the first Republican hopeful to begin running radio and TV ads, launching his ad campaign before Christmas. But a poll showed that about two-thirds of Republican voters in the state are unsure who he is.