Over the past six weeks, a proposed constitutional amendment that would end same-sex marriage in California has gained substantial ground but still trails by a five-point margin heading into Tuesday's election.

A new Field Poll shows Proposition 8, one of the most closely watched state ballot measures in years, is supported by 44 percent of likely voters. Forty-nine percent oppose it, and 7 percent are undecided.

In the last Field Poll, released Sept. 18, the measure was behind by 17 points.

"It's certainly closer than it was before the advertising campaign hit," said Field Poll director Mark DiCamillo. "A lot of that has to do with the campaigning on the Yes (on 8) side."

In television ads, supporters have expanded their arguments beyond the issue of whether gay couples should be allowed to marry to warn that schools would incorporate same-sex marriage into lesson plans.

Opponents have dismissed those claims as scare tactics. They've argued that by eliminating the right of gays to marry, the measure would deprive one group of a freedom enjoyed by another group.

As the debate has intensified, many supporters and opponents have taken a closer look at the measure – and in some cases been persuaded by arguments from the other side, DiCamillo said.

"The ('Yes') campaign has been effective, but will it be enough?" he said.

Nearly half of all voters are voting early or by mail, and they narrowly favor Proposition 8 by a three-point margin, according to the poll. Among the 22 percent of respondents who have already voted, the yes side was leading by six points.

But DiCamillo said the survey also suggests that the no side has enough supporters to defeat the measure and the race will come down to which side gets more of its backers to the polls on Election Day.

Voters supporting Democrat Barack Obama for president overwhelmingly oppose Proposition 8, and those backing Republican John McCain overwhelmingly support it, according to the poll.

A Field Poll released earlier this week showed Obama leading McCain in California by a whopping 22 points.

DiCamillo said that has been factored into the Proposition 8 poll, which means that if Obama wins by a larger margin, the "No" side will benefit. The same is true for the "Yes" side if McCain beats expectations.

Geography is also playing an important role. Voters who live in coastal California counties constitute 71 percent of likely voters, and they oppose the measure by a 54-39 margin, according to the poll. Those who live in inland counties back it by a 57-37 margin.

"This poll is showing the (Central Valley) strongly on the 'Yes' side," DiCamillo said. "It's just the rest of the state – the coastal counties – that is heavily on the 'No' side."

One Sacramentan who has already voted against the measure is Carol Johnson, a lesbian who doesn't understand why opponents of gay marriage feel threatened.

"It has nothing to do with their marriage, which is probably rocky," Johnson said. "My friend Dave, who's straight, was saying we should put up a Defense of Marriage Act and anybody who gets caught in adultery gets beaten in the public square."

But another Sacramentan, Kirk McCorris, said he is voting for the measure because of his Christian beliefs.

He is also angry that the California Supreme Court overturned a ballot measure overwhelmingly approved by voters in 2000 that banned same-sex marriage.

"Sixty-one percent of voters approved it, and yet four judges disregarded their views," McCorris said.

The latest Field Poll also found Proposition 2 leading by a commanding 33-point margin, 60 percent to 27 percent, with 13 percent undecided. The measure effectively would ban farms in California from confining egg-laying hens, breeding pigs and veal calves in cages or crates.

Proposition 11, which would strip legislators of the power to draw legislative districts and hand that responsibility to an independent commission, was leading by 15 points, 45 percent to 30 percent, with 25 percent undecided.

Proposition 7, which would require all California utilities to get at least half their electricity from clean, renewable sources, was trailing by four points.

Call Aurelio Rojas, Bee Capitol Bureau, (916) 326-5545.