Amid roaring chants from supporters and tears from opponents, the state Senate took a historic step Monday to legalize same-sex marriage in Minnesota.

The 37-30 vote came after a failed, last-ditch attempt by opponents to scuttle the measure.

“I’m going to be a married man in Minnesota!” DFL Sen. Scott Dibble, the Senate’s only openly gay member, proclaimed to supporters after emerging from the chamber.

One Republican, Sen. Branden Petersen, joined a majority of DFL legislators to make Minnesota poised to become the 12th state to legalize gay marriage. Three DFLers voted against the measure.

Sen. Dan Hall, R-Burnsville, pleaded with colleagues to vote the bill down: “Don’t vote what you know is morally wrong,” said Hall, a former CEO of Midwest Chaplains. “May God help us.”

Minnesota will become the first Midwestern state to legalize same-sex marriage by legislative vote, and it signals the latest victory for those working to extend marriage rights to gay and lesbian couples across the nation. Monday’s action technically repeals a state statute that had prohibited such unions.

Gov. Mark Dayton will sign the bill at 5 p.m. Tuesday, on the Capitol steps, kicking off a parade that will take supporters to a massive downtown St. Paul celebration. The law will take effect Aug. 1.

Opponents said the vote is a testament to the political muscle of gay and lesbian advocacy groups.

“It’s amazing what you can do when you have the resources,” said John Helmberger, chairman of Minnesota for Marriage, the lead group that worked to block same-sex marriage from being recognized. “This is definitely not the will of the people.”

The vote completes a seismic turnaround on the issue in Minnesota. Two years ago, Republicans controlled the Legislature and put a constitutional measure on the ballot to ban same-sex marriage.

That triggered the formation of Minnesotans United for All Families, an advocacy group that generated unprecedented financial and volunteer support to campaign against the measure, which was defeated last November.

This year, the group unleashed its lobbying might to press the Legislature, now under Democratic control, to legalize same-sex marriage.

“The irony of today, as great as it is, is that if the Republican majorities two years ago had not placed this on the ballot in November, we wouldn’t be here today,” said Sen. Dick Cohen, a St. Paul DFLer who was a chief backer of the marriage measure. “The two-year buildup for that is what has allowed this to happen.”

Throughout the day, a throng of 3,000 same-sex marriage supporters, countered by a handful of opponents, jammed nearly every corner of the Capitol.

The tenor was vastly different from the uncertainty that hung over last week’s House vote on the issue. Monday’s vote drew a younger, more celebratory crowd, with few of the intense showdowns that erupted while the House debated the issue.

Al Mack of Coon Rapids and Alec Fischer of Edina held up orange signs with the words: “My boyfriend,” and arrows pointing at one another. “We shouldn’t be treated as second-class citizens,” Mack said.

Gay and lesbian couples held hands as they waited confidently for the vote, snapped pictures of one another and ambled through the halls, some pushing strollers with young children.

Hundreds of heterosexual supporters showed up too, wearing shirts and holding signs that said “Support Marriage.” Many members of the crowd joined in singing “Amazing Grace” and “We Shall Overcome.”

In the rotunda, Minneapolis Mayor R.T. Rybak shouted over the railing to the people below: “It takes five days to get a marriage license in Minnesota!” To rousing cheers he added, “August 6th, come on down to City Hall.”

‘Be bold, be courageous’

Inside the usually somber Senate chambers, members shared intensely personal stories about family, friends and loved ones who are gay or lesbian as they took turns speaking on the bill.

Petersen, the only Republican in the body to support same-sex marriage, found himself a national villain with those who thought he betrayed his party.

Petersen acknowledged the vote could cost him his seat, but closed with parting advice to his young children: “Be bold, be courageous, and you will never regret it a day in your life.”

Among the Democrats, LeRoy Stumpf of Plummer, Dan Sparks of Austin and Lyle Koenen of Clara City went against their party and voted no.

Sparks said he’d had “many sleepless nights over this one.” He said his decision came at the last minute, as he thought about the strong opposition to gay marriage within his district.

“It’s by far the toughest vote I’ve had to cast in my 11 years in the Senate,” he said.

However they voted, legislators agreed that there is no turning back on what they now see as a settled issue in the state.

“This is the civil rights issue of our generation,” said Sen. Ron Latz, DFL-St. Louis Park.

‘I can’t believe it’

The Capitol erupted in deafening celebration after the vote. Even Senate staffers, secretaries and aides who had seen other big moments in the chamber couldn’t contain their applause.

Anita Rentz and Carol Klein, 28-year partners from East Bethel, fell into a long, tearful embrace.

“Oh my gosh, I can’t believe it,” Rentz said. “This is just so wonderful. I never thought I’d see it in my lifetime.” Klein is 80 and Rentz, 62, and they were not sure they would ever make it to the altar. They now plan to marry soon.

Nearby, a lone anti-gay-marriage crusader, Linda Sevlie of Coon Rapids, raised her “one man one woman” sign. She looked on stoically at the singing, dancing and chanting that had erupted around her.

“It’s a sad day for Minnesota,” Sevlie said, straining to be heard above the din. “But God is in charge, although I do believe there are tears in heaven.”

The thousands of elated supporters radiated outward from the North Star emblem in the Capitol rotunda and filled the upper railings. A sign reading “Marriage Equality — You Betcha” hung from the second floor and seemed to serve as an exclamation point to their revelry.

“We’re number 12!” the crowd chanted.

Joellen Barak of St. Charles called it a great day for Minnesota. “It will mean that I live in a state that appreciates diversity and equality,” she said.

Out on the Capitol steps, some opponents lingered, waving signs and praying together.

Nick Skrynnik of Plymouth held a sign reading, “Proud father of a God-approved family.”

“Once it becomes a law, it’ll be taught in schools. It’ll be forced on to my children, to make them believe that this is OK,” he said. “And me on the other hand, telling them this is not OK according to God’s word.”

Down in the Great Hall, the Rev. Pat Hall, an opponent of the bill and brother of state Sen. Dan Hall, said it had been his hope that a solution could be found that both sides would find acceptable.

“I think we are as divided now as we were during the Civil War,” he said.

For Ellen Rowell, though, the vote brought a sigh of relief.

Rowell has been raising a son in south Minneapolis with her lesbian partner of 15 years.

“We’ve lived our lives, we’ve raised our son, we’ve done PTA, basketball games, all these years, but we haven’t had a legal relationship,” Rowell said. “It’s just time.”