Mr. Pawlenty’s spokesman said the former governor and his wife “chose to express their commitment to the institution of marriage using their own words in a video about their values and faith. We appreciate the opportunity but respectfully decline to sign the pledge.” (The video, released in July, is here.)

Earlier this summer, Mr. Pawlenty declined to sign an anti-gay-marriage pledge pushed by Iowa activist Bob Vander Plaats, saying that “rather than sign onto the words chosen by others, I prefer to choose my own words, especially seeking to show compassion to those who are in broken families through no fault of their own.”

Mr. Romney also refused to sign the earlier pledge, calling it “undignified and inappropriate.” Mr. Santorum and Ms. Bachmann did sign that pledge.