Delaware Senator Tom Carper on Tuesday became the latest Democratic senator to endorse gay marriage.

Carper said in a Facebook post that he believes the Golden Rule applies to the issue.

“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.”

An online petition asking Carper to support marriage equality attracted more than 150 signatures.

“Only a handful of Democratic U.S. Senators do not support marriage equality for same-sex couples and Delaware's Tom Carper is one of that tiny minority,” Ezra J. Tempko's petition states. “My marriage to my husband should be treated equally under the law, and the same is true for other same-sex couples throughout our state and nation.”

Delaware recognizes gay and lesbian couples with civil unions, but lawmakers are expected to debate a marriage equality bill this legislative session.

Carper joins a growing list of U.S. senators who have recently reversed course on the issue, including Senator Rob Portman, a Republican from Ohio, and Democratic Senators Claire McCaskill of Missouri, Mark Warner of Virginia, Mark Begich of Alaska, Jon Tester of Montana, Jay Rockefeller of West Virginia, Kay Hagan of North Carolina and Bob Casey of Pennsylvania.

Only seven Democratic senators remain opposed to marriage equality, they are: Mark Pryor of Arkansas, Joe Donnelly of Indiana, Bill Nelson of Florida, Joe Manchin of West Virginia, Mary Landrieu of Louisiana, Heidi Heitkamp of North Dakota and Tim Johnson of South Dakota.