Kirsten Lindbloom looked out at the crowd of smiling faces and rainbow flags gathered on the State Capitol steps on Thursday and laughed.

"For crying out loud, people," she said. "Iowa's got this figured out."

This November, Minnesotans will be asked to vote on a constitutional amendment that would define marriage as the union of a man and a woman -- essentially banning gay marriage.

Amendment supporters believe they have the Bible, the poll numbers and statistical probability on their side. To date, gay marriage bans have passed in every state where they have appeared on the ballot.

Thursday's rally in St. Paul marks the start of a coordinated effort by opponents to make Minnesota the exception, led by Gov. Mark Dayton.

"I dreamt ... that Minnesota would be the first state in the nation to reject" a constitutional ban on gay marriage, Dayton told a cheering crowd that included gay and straight men and women, clergy and families with small children. "I think Minnesota's better than that," Dayton said from a riser in front of the Capitol.

Below, the crowd erupted into cheers and waved signs with slogans like, "I'm straight, but not narrow," and "Closets are for clothes. Fabulous, fabulous clothes."

Thursday was a day of action for two of the groups at the forefront of the Just Vote No movement -- OutFront Minnesota and Minnesotans United for All Families. Participants spent the morning learning community organizing techniques and preparing to spend the afternoon lobbying lawmakers against the amendment, which will appear on the November ballot.

But Chuck Darrell, director of communications for Minnesotans for Marriage, said those who believe that marriage should be reserved for a union between a man and a woman are mobilizing as well.

"They're holding rallies," he said of the amendment opponents. "We're going directly to our base. And we're very pleased by the enthusiastic reaction we're getting."

Darrell said gay marriage opponents are reaching out to African-American, Latino, Somali, Jewish and Islamic communities in Minnesota to make their case for traditional marriage. They are organizing call centers and online videos. But large-scale rallies, he said, "aren't in our future."

The Just Vote No movement, meanwhile, is mobilizing a door-to-door canvassing campaign in the Twin Cities this weekend, trying to drive home the message that supporters need to vote against the constitutional amendment if they want to support gay marriage. The annual Twin Cities Pride Festival in June also will be a major rallying event for the movement.

At Thursday's noon rally, Justin Anderson, a 19-year-old graduate of the Anoka-Hennepin school system, described the relentless bullying he endured from middle school through graduation. The gay slurs and taunts got worse, he said, when California voters enacted an amendment that forbids gay marriages.

He worries what will happen to gay youngsters if Minnesota does the same thing.

"One time in eighth grade, a student said to my face, about five feet from a teacher, 'Gays should go kill themselves, so we don't have to deal with them anymore,' " Anderson said. "And the teacher's response was, 'Quiet. You can't talk during class time.' "

Lindbloom, who lives in Austin, said she thinks lawmakers "underestimate the number of people in the boonies who are gay and lesbian." Her partner, Ginny Larsen, is battling cancer, and she wants to see their union recognized by their state.

"I'm a woman who's about to lose her wife," Lindbloom said. "We're running out of time."

Jennifer Brooks • 651-925-5049