The head of a think tank on marriage and family testified at the Proposition 8 federal trial today that same-sex marriage would weaken marriage and possibly lead to fewer heterosexual marriages, more divorces and “more public consideration of polygamy.”

But under cross examination, David Blankenhorn, founder and president of the Institute for American Values, acknowledged that he wrote in a book in 2007 that the U.S. would be “more American on the day we permit same-sex marriage than we were on the day before.”

Blankenhorn was called as an expert witness by lawyers defending Proposition 8 against a constitutional challenge by two same-sex couples. He is an author and researcher who is not associated with any university. He earned a master’s degree in history in England, where he studied the history of labor unions.

Read the rest of Maura Dolan’s LA Times article here.