Sen. Tom Carper (D-Del.) on Tuesday became the latest Democratic senator to announce his support for gay marriage.

Carper said on his Facebook page that his position has evolved on the issue as he has talked to friends and family and that he believes the Golden Rule applies to gay marriage.

"It calls on us to treat others as we want to be treated," Carper said. "That means, to me, that all Americans ultimately should be free to marry the people they love and intend to share their lives with, regardless of their sexual orientation, and that's why today, after a great deal of soul searching, I'm endorsing marriage equality."

Carper joins Sen. Bob Casey (D-Pa.) in coming out in support of gay marriage this week. Several others did so last week, and Sen. Rob Portman (R-Ohio) became the first Republican senator to back gay marriage last month.

There are now just seven Democratic senators who have yet to endorse gay marriage, with six of them hailing from red states. The holdouts are: Joe Donnelly (Ind.), Heidi Heitkamp (N.D.), Tim Johnson (S.D.), Mary Landrieu (La.), Joe Manchin (W.V.), Bill Nelson (Fla.) and Mark Pryor (Ark.).

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