California's Supreme court has set a hearing date of March 5 for oral arguments in a series of lawsuits seeking to overturn Proposition 8.

Gay couples and several local governments maintain the ballot initiative is unconstitutional.

If the measure is upheld, the court said it will also decide whether the 18,000 same-sex marriages performed when gay marriage was legal in California are valid.

The court's seven justices will have 90 days to issue a ruling after hearing arguments.

Most Expensive Ballot Measure in U.S. History

The final tallies on California's Proposition 8 show it was by far the most expensive ballot measure on a social issue in the nation's history.

Campaign filings released this week report more than $83 million was raised to support or oppose the marriage amendment.

Prop 8 opponents gave the most with a total of $43.3 million, while supporters raised close to $40 million.

The report also lists 500 small donors, previously unreported, who supported Prop 8 at the end of the campaign.

Prop 8 sponsors had asked that their names not be released, for fear of harrassment.  But a federal judge overruled their request.