Opponents of gay marriage are once again promoting the narrative that legalizing marriage for gay and lesbian couples would harm children.

The tactic is being used in ads produced in four states by the National Organization for Marriage (NOM).

Referendums in Maryland and Washington state ask voters to uphold gay marriage laws approved by lawmakers. Minnesota will vote on a constitutional amendment which would limit marriage to heterosexual couples. And Mainers on November 6 will decide whether to legalize such unions.

Frank Schubert is the chief strategist of the four ballot fights. He ran California's 2008 Proposition 8 campaign, which overruled a state Supreme Court ruling legalizing marriage for gay men and women. He repeated that success in Maine the following year and North Carolina in May.

Schubert dreamed up the legendary “Princess Ad” during the Proposition 8 campaign. In the ad, a young girl tells her mother that she learned at school “how a prince married a prince, and I can marry a princess.”

In the final weeks of the campaigns, Schubert has released similar ads in all four states highlighting the plight of David and Tonia Parker, the Massachusetts couple who objected to the inclusion of the book Who's in a Family? in their son's public school lessons.

“If marriage is redefined in Minnesota, same-sex marriage could be taught in local Minnesota schools, just like it was in Massachusetts,” Mrs. Parker says in the ad airing in Minnesota. “Don't make the same mistake and think that gay marriage won't affect you.” (The video is embedded on this page. Visit our video library for more videos.)

The ads are yet another example of the increasingly hyperbolic tone opponents have taken in the final weeks. For example, in Maryland a pastor associated with the campaign suggested gay people and their allies are “worthy of death.” And in Minnesota, Pastor Brad Brandon accused marriage equality supporters of suppressing the religious freedom of opponents with techniques similar to those used by Adolf Hitler.