SACRAMENTO – A majority of California voters oppose a ballot initiative to ban gay marriage, though they are evenly split on the practice itself, according to a poll released Wednesday.

The ballot question essentially will ask voters to prohibit the practice of same-sex marriage, which was approved this year by the California Supreme Court.

The discrepancy between voters' general attitudes against gay marriage and their position on banning it could be explained by a hesitancy to remove a constitutional right, said Mark Baldassare, president and chief executive of the Public Policy Institute of California, which conducted the poll.

A majority of likely voters, 54 percent, oppose ending gay marriage, compared with 40 percent who support it, the poll said. The result is similar to the findings of a Field Poll in July, which found that 51 percent of likely California voters opposed ending gay marriage, while 42 percent said they supported it.

But when it comes to general attitudes about gay marriage, voters in the Public Policy Institute poll are evenly split, at 47 percent for and against – as they have been for the past three years.

“It's early in the campaign season, and in the end the vote on this measure ... could be hard to predict,” Baldassare said. “Overall views on gay marriage have not budged.”

The Public Policy Institute began asking voters how they feel about gay marriage in 2000, the year voters approved an initiative to ban same-sex marriage but did not enshrine it in the Constitution. That year, the poll found 55 percent opposed to gay marriage and 38 percent in favor.

In May, the state Supreme Court ruled the 2000 initiative unconstitutional, opening the door to same-sex weddings throughout the state.

The new poll indicates that those opposed to gay marriage will have to mobilize voters if they are to be successful in November, Baldassare said.

“The burden is always on the yes side to convince people there is good reason to vote for the measure,” he said.

The institute surveyed 2,001 California residents, including 1,047 likely voters, in English and Spanish from Aug. 12 to 19. The poll has a margin of sampling of error of 2 percentage points for all residents and 3 percentage points for likely voters.

Associated Press writer Lisa Leff in San Francisco contributed to this report.