A prominent segment of the Republican base, social conservatives helped elect George W. Bush in 2004, and social-conservative activists have exerted a powerful influence over the Iowa GOP caucuses, a key hurdle for Republican presidential contenders, which surprised many by handing victories to Mike Huckabee in 2008 and Rick Santorum in 2012.
One signature that was noticeably missing from the letter was that of leading social conservative Bob Vander Plaats. Vander Plaats led socially conservative initiatives in Iowa through his Family Leader organization and gives his full support to the views expressed in the letter.
"If I was asked to sign the letter, I definitely would have," Vander Plaats told ABC News.
"A lot of people in the party are concerned that the party will sell out our values in order to win, and if you do that what do you really win?" he continued.
Vander Plaats also agreed with the prediction that the GOP would lose support if it follows the recommendations of the "Growth and Oppotunity Project" to the letter.
If Republcians "abandon their values, people will abandon their party," he said. "Republicans are motivated by issues, not by the Republican name ... and these issues aren't going to change regardless of what the poll numbers say."