Zach Wahls on Monday kicked off a week-long campaign urging Minnesotans to vote against a proposed constitutional amendment defining marriage as a heterosexual union.

Wahls is the University of Iowa student who defended his two-mom family at an Iowa House hearing considering a proposed measure which would repeal the state's gay marriage law by defining marriage as a heterosexual union in the Iowa Constitution. A video of Wahls' testimony attracted more than 18.3 million views to become the most-watched video in 2011.

Wahls, now 21, also authored a memoir about his two-mom family titled My Two Moms: Lessons of Love, Strength, and What Makes a Family.

Wahls' first stop was the Minnesota State Fair, where he helped man the booth of Minnesotans United for All Families, the coalition of groups working against passage of the amendment. Later in the day, he spoke at the 19th annual Duluth Labor Day Picnic.

On Tuesday, Wahls will help launch the University of Minnesota Duluth group UMD Students United for All Families. And later in the week, he is scheduled to speak to students at St. Cloud State University and the University of Minnesota.