Republican Tim Pawlenty says he won't sign a pledge written by a conservative Iowa group that asks presidential candidates to denounce same-sex marriage rights, pornography and forms of Islamic law.

Pawlenty said Wednesday he agrees with the principles behind the Family Leader's Marriage Vow. But he says he prefers "to choose my own words, especially seeking to show compassion to those who are in broken families through no fault of their own."

The former Minnesota governor is the second major candidate to decline the pledge, following former Massachusetts Gov. Mitt Romney's decision Tuesday. Two Republicans, Minnesota Rep. Michele Bachmann and former Pennsylvania Sen. Rick Santorum, have signed it.

Pawlenty's announcement coincides with the release of a new radio ad and web video where he and his wife discuss their faith.