Another Senate Democrat, Sen. Bob Casey of Pennsylvania, came out today in support of same-sex marriage.

"After much deliberation and after reviewing the legal, public policy, and civil rights questions presented, I support marriage equality for same-sex couples and believe that DOMA should be repealed," Casey said in a statement.

The senator says letters he received from LGBT couples challenged him directly and "had a substantial impact on my position on this issue."

"If two people of the same sex fall in love and want to marry, why would our government stand in their way? At a time when many Americans lament a lack of commitment in our society between married men and women, why would we want less commitment and fewer strong marriages? If two people of the same sex want to raise children, why would our government prevent them from doing so, especially when so many children have only one parent, or none at all?" Casey asked in his statement.

Casey's flip on the issue marks the seventh Senate Democrat in a week to reverse course and embrace same-sex marriage. There are only eight Senate Democrats left who continue to oppose marriage equality.

Those eight senators are Heidi Heitkamp of North Dakota, Joe Manchin of West Virginia, Mary Landrieu of Louisiana, Joe Donnelly of Indiana, Mark Pryor of Arkansas, Tom Carper of Delaware, Bill Nelson of Florida and Tim Johnson of South Dakota.