After originally leaving his name off, Republican presidential candidate Tim Pawlenty has signed a national group's pledge to seek a federal constitutional amendment outlawing same-sex marriage.

Pawlenty spokesman Alex Conant said Friday that made the commitment to the National Organization for Marriage after taking time to review the pledge. A group leader had voiced concern when the former Minnesota governor didn't sign earlier.

Former Massachusetts Gov. Mitt Romney, Minnesota Rep. Michele Bachmann and former Pennsylvania Sen. Rick Santorum all took the pledge to "support and send to the states" an amendment defining marriage as between a man and a woman. They also agreed to defend traditional marriage from legal challenges.

Pawlenty and Romney announced earlier this summer they wouldn't sign an Iowa conservative group's more expansive pledge on marriage.