Sen. Rob Portman, R-Ohio, announced last week that he now supports gay marriage after learning one of his sons was gay.
Rove's comment was part of a panel discussion on ABC's "This Week." He did not elaborate.
The Supreme Court is taking up two cases this week involving same-sex marriage. Tony Perkins, president of the Family Research Council, told CBS' "Face the Nation" that most Republicans still oppose gay marriage and noted that 30 states have defined marriage between a man and a woman.