Lady Gaga and Brad Pitt have weighed in on one side, evangelist icon Billy Graham on the other as the four-state showdown over same-sex marriage reaches its Election Day conclusion with the potential for a historic breakthrough.
Until now, same-sex marriage has been rejected in all 32 states that have held popular votes on the issue. Gay-rights advocates believe they have a chance to break that streak as Maine, Maryland and Washington state vote on whether to legalize same-sex marriage, and Minnesota votes on whether to place a ban on gay marriage in the state constitution.
In all, there are 176 measures on the ballots in 38 states, according to the Initiative and Referendum Institute at the University of Southern California. Washington, Oregon and Colorado could become the first to legalize recreational use of marijuana; Massachusetts is considering whether to allow physician-assisted suicide; Californians have a chance to repeal the death penalty.
But no other issue has generated the star power or multistate intensity of the same-sex marriage measures.
In just the past week, Lady Gaga released a video backing same-sex marriage, while Pitt donated $100,000 to support the cause. On the other side, Graham, 93, took out newspaper ads asking voters to support ‘‘the biblical definition of marriage between a man and a woman.’’
President Barack Obama also has entered the debate, endorsing the three gay-marriage measures and urging a ‘‘No’’ vote on the proposed ban in Minnesota.
Brian Brown of the National Organization for Marriage, which has spent more than $5.5 million in the four states opposing same-sex marriage, predicted Obama’s stance wouldn’t be enough to break the 32-state streak.
‘‘People’s personal conviction that marriage is the union of husband and wife is too strong to be swayed by what the president says,’’ Brown said.
All four elections are expected to be close. In Maine, the latest poll showed gay-marriage supporters with a lead of 13 percentage points, down from a 21-point lead in September.
The referendum in Maine marks the first time that gay-marriage supporters have put the issue to a popular vote there. They collected enough signatures over the summer to schedule the vote, hoping to reverse the outcome of a 2009 referendum that quashed a gay-marriage law enacted by the Legislature.
A TV ad by gay-marriage supporters in Maine featured Republican state Rep. Stacey Fitts, who was opposed in 2009 but now plans to vote for it.
‘‘Society in general has come to the idea of why would we ostracize people for something that’s part of who they are,’’ Fitts said.
In both Maryland and Washington, gay-marriage laws were approved by lawmakers and signed by the governors earlier this year, but opponents gathered enough signatures to challenge the laws.
In Minnesota, the question is whether the state will join 30 others in placing a ban on gay marriage in its constitution. Even if the ban is defeated, same-sex marriage will remain illegal under a current statute in Minnesota.
Gay marriage is legal in six states and the District of Columbia — in each case the result of legislation or court orders, not by a vote of the people.
Of the other issues on the ballot in multiple states, marijuana is perhaps the highest-profile.
Voters in Washington, Oregon and Colorado have a chance to do what no state has done before — legalize the recreational use of pot by allowing adults to possess small amounts under a regimen of state regulation and taxation. The Oregon proposal has lagged, but the Washington and Colorado measures have a decent chance of passage.
If approved, the measures would set up a direct challenge to federal drug law.
‘‘If one of these initiatives passes, it will be a watershed moment in the decades-long struggle to end failed marijuana prohibition policies in this country,’’ said Ethan Nadelmann of the Drug Policy Alliance, a critic of the so-called war on drugs.
In Arkansas and Massachusetts, voters will be deciding whether to allow marijuana use for medical reasons, as 17 states have done previously. Arkansas would be the first Southern state to join the group.
Other notable ballot measures:
—Massachusetts could join Oregon and Washington in allowing terminally ill patients to obtain lethal doses of medication if doctors say they have six months or less to live.
—California voters could repeal their state’s death penalty. If approved, the 720-plus inmates on death row there would have their sentences converted to life in prison.
—Another contentious measure in California would require most genetically engineered processed foods sold in supermarkets and other outlets to be labeled as such.
—California labor unions are the target of a measure aimed at depriving them of tens of millions of dollars they use to finance campaigns and political organizing. Proposition 32 would prohibit them from collecting money for state political activities from members through paycheck deductions.
—In Michigan, labor unions succeeded in getting a vote on a first-of-its-kind ballot initiative that would put collective bargaining rights in the state constitution.
—In Alabama, Montana, Florida and Wyoming, voters will weigh in on a key aspect of Obama’s health care overhaul in the form of Republican-backed measures stating that no individual or business can be forced to participate in a health care system. The measures would violate federal law and attempts to enforce them would probably wind up in court.
—Maryland voters will decide whether to uphold a new state law allowing some illegal immigrants to pay in-state tuition at public colleges.
—A measure in Montana would require people who receive certain state services to provide proof of U.S. citizenship or legal residency.
—Oklahoma voters will decide whether to abolish affirmative action programs in state government and education.
—Minnesotans will decide on an amendment that would require showing a photo ID in order to vote.
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