The Minnesota Senate, after four hours of floor discussion Monday, joined the state House of Representatives in approving same-sex marriage.

The measure, which could be signed as early as Tuesday by Gov. Mark Dayton, means Minnesota will become the 12th state in the nation to permit gay marriages.

The Senate vote was 37 to 30. The Minnesota House passed the measure Thursday on a 75-59 vote.

Moments before the vote, chief author Sen. Scott Dibble read passages of a poem by Langston Hughes. “Let America be America again,” Dibble said. “Let it be the dream it used to be.”

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The vote came after more than four hours of emotional and at times acrimonious debate. Near the end, the din from supporters and opponents sometimes threatened to drown out the floor speeches.

Inside the chamber, opponents prayed and held rosaries and Bibles while supporters held hands and blotted tears. Capitol staff packed the Senate floor as Dibble took up the microphone — a traditional signal under legislative protocol that a vote is imminent.

The action comes just six months after Minnesota voters rejected a proposed constitutional amendment that would have defined marriage as only between one man and one woman. And it takes place just one week shy of the second anniversary of the Legislature’s vote to place the proposed ban on gay marriage in the state constitution.