ST. PAUL — Lawmakers formally launched a long-anticipated effort Wednesday to legalize gay marriage in Minnesota by summer, and gay couples and their small children crowded the kickoff news conference — a visual reminder that family diversity exists in the state but is not recognized by its laws.

Arguing that such families deserve the same recognition from the state as more traditional ones, sponsors of the gay marriage bill aim to repeal Minnesota’s 1997 law that prohibited marriage between couples of the same sex. The bill exempts churches from being forced to perform same-sex weddings.

“We’re a family in the eyes of God,” Michael Adam Latz, a Minneapolis rabbi raising two daughters with his male partner. “But right here in my home state of Minnesota, the place where I was born, where we live, work, pay taxes and raise our children, we are legal strangers.”

Gay marriage supporters point to last fall’s defeat of the constitutional gay marriage ban as the starting point for what they hope is a final push to legalize it. Gov. Mark Dayton has said he would sign the bill if it reaches his desk; if that happens, same-sex weddings would commence on Aug. 1.

But Republicans opposed to gay marriage said supporters got the wrong message from defeat of the marriage amendment.

“The people simply said they didn’t want to take the definition of marriage as it’s written in Minnesota state law, and include that in the constitution,” said Sen. Warren Limmer, R-Maple Grove.

The bill would change Minnesota’s current statutory definition of marriage from “a civil contract between a man and a woman” to “between two people.” The bill would exempt churches from being forced to perform same-sex weddings.

“Communities of conscience and others in Minnesota who may disagree with this bill won’t be compelled to do anything, won’t be required to violate their own conscience,” said Rep. Steve Simon, DFL-St. Louis Park, a co-sponsor of the bill.

But Sen. Dan Hall, a Burnsville Republican and a pastor, said he worried that exemption could be lifted in future legislative sessions. “I will personally go to jail before I ever perform a marriage for a homosexual,” Hall said. Republicans said they were also worried that business owners who cater to weddings could face consequences if they refuse on moral grounds to do business with gay couples.

It has been a long road for gay Minnesotans seeking the right to get married.

The state Supreme Court ruled against gay marriage back in 1971. In 1997, when the Legislature was under Democratic control, lawmakers strengthened that prohibition by overwhelmingly passing a “Defense of Marriage Act.”

By 2004, conservative activists were seeking an even stricter ban. Michele Bachmann, then a state senator, initiated a multi-year effort to put a constitutional gay marriage ban before voters statewide. It finally reached fruition in 2011, when Republicans in control of both legislative chambers voted the amendment onto the ballot.

The amendment failed by about 150,000 votes after a long and expensive campaign, on an Election Day that saw three other states vote affirmatively for gay marriage. Those results were widely seen as a turning point for gay marriage supporters after years of electoral setbacks nationwide.

“It was a very clear statement,” said Rep. Karen Clark, DFL-Minneapolis, the bill’s chief House sponsor. Gay marriage is now legal in nine U.S. states, and a bill to legalize it in Illinois is moving through that state’s Legislature.

But the amendment’s defeat left gay marriage still illegal under existing Minnesota statute. With the governor’s office and Legislature under Democratic control after the 2012 election, gay marriage backers had the optimal political landscape for their push.

The bill’s chief Senate sponsor, Minneapolis Democrat Scott Dibble, rejected the idea that the amendment campaign pivoted on whether the gay marriage ban should be in the constitution.

“The conversation was, ‘What is marriage all about? Why does marriage matter?’ We argued that marriage is for everyone, freedom is for everyone, love is love and a commitment is for a lifetime,” Dibble said. “My sense is that Minnesotans have come so far, so fast on this issue and the Legislature is ready to settle this question and move on.”

Dibble said he doesn’t yet know if the votes are there to pass the bill, but added, “I think we’re close.” House and Senate committees plan hearings in March; final votes could come in April or May.

So far, only one Republican lawmaker publicly supports the bill: Sen. Branden Petersen, R-Andover. Clark said she believed other Republicans would get on board.

Pat Anderson, a Republican former state auditor and party official, published an essay in Wednesday’s St. Paul Pioneer Press supporting gay marriage.

“This is a limited government issue,” Anderson said. “The question is: What is government’s role in the marriage issue? I would say it should be limited.”

But the GOP still has strong reservations.

“There is no gay gene. OK?” said Rep. Glenn Gruenhagen, R-Glencoe. “So the concept that you’re born that way and it’s an immutable characteristic is an unscientific lie.”

The American Psychological Association declared in 2009 that there’s no scientific consensus about why an individual develops a specific sexual orientation. But the group also said most people experience no sense of choice over their sexual orientation, and advised members not to counsel patients that homosexuality can be changed.

Some legislative Democrats face a tough vote on gay marriage, representing legislative districts where voters backed last fall’s amendment. By the same token, some Republicans hail from districts that voted it down.

Rep. John Ward, DFL-Baxter, represents a Brainerd-area district that supported the amendment by nearly 15 percentage points.

“I’m undecided,” Ward said Wednesday. “My main focus is the budget, and I want to take care of that before we start worrying about these hot-button issues.”