Two Unitarian-Universalist ministers are riding on the "Marriage Equality" Caravan, whose goals are "to focus attention on proposed amendments to write discrimination into both state constitutions and the U.S. Constitution, and 'to demand a repeal of anti-gay measures like the Defense of Marriage Act and Don't Ask, Don't Tell.' "
Bear in mind that these ministers are reprensentatives of a liberal denomination that believes in the separation of church and state so much that some of its members are trying to revoke the tax-exempt status of churches trying to promote the Federal Marriage Amendment. Now of course, the participation of two ministers is not exactly an explicit endorsement by the denomination, but on the other hand, the link is from the UUA website which implies that the denomination is promoting their cause. Here's another link showing that UUA support for gay marriage goes as far as explicit and extensive political lobbying.