A new poll has Mitt Romney edging out Newt Gingrich as the most trusted GOP presidential candidate on gay marriage.

According to the Washington Post/ABC News poll released Tuesday, 25 percent of Republicans say they trust Romney the most with social issues such as abortion and gay marriage. Gingrich trails with 15 percent, followed by Rick Santorum (14%), Ron Paul (10%), Rick Perry (9%) and Jon Huntsman (3%). Six percent of respondents said they did not trust any of the candidates on social issues.

(Related: Jon Huntsman endorses Mitt Romney as he steps out of GOP race.)

Santorum and Perry were the only two candidates whose polling numbers increased from last month's survey. Santorum was up by 10 points, while Perry enjoyed a more moderate 2 percent bump.

Romney has said he favors an amendment to the U.S. Constitution which would define marriage as between a man and a woman.

At a town hall in October, Romney said he opposed marriage for gay couples because “the ideal setting to raise a child for a society like ours is when there's a man and a woman in the marriage.”

When pressed on civil unions, Romney said he could only support a limited partnership for gay couples which would include “such things as hospital visitation rights and similar things.”

Santorum frequently discusses his opposition to marriage equality. Campaigning in early caucus state Iowa, where the institution is legal, he often used inanimate objects to refer to such unions. In Iowa Falls, he said paper towels are not napkins; and during an interview with the Iowa Independent he said trees are not cars in explaining his position. He has also suggested that gay marriage has wrecked the economy.