SACRAMENTO, Calif. – A slight majority of California voters oppose a measure on the Nov. 4 ballot that would impose a constitutional ban on gay marriage, according to the first Field Poll on the measure.

The findings are consistent with a May poll on the issue before Proposition 8 qualified for the ballot. The issue has received heightened attention since the state Supreme Court in May struck down a law approved by voters in 2000 that banned gay marriages.

This time, Californians likely to vote in the Nov. 4 election were asked specifically about Proposition 8, which would enshrine in the state constitution that only marriage between a man and a woman is valid or recognized in California.

Fifty-one percent of respondents said they oppose the proposed ban; 42 percent support it; and 7 percent are undecided.

While voters overwhelmingly approved Proposition 22, the statute that banned gay marriage in 2000, the new poll suggests a “reluctance by Californians to tinker with the constitution,” said Mark DiCamillo, director of the Field Poll.

“Older voters, especially, are more reticent about changing the constitution where younger folks are more in favor of allowing same-sex marriage,” DiCamillo.

The highest percentage of respondents who opposed Proposition 8 in the poll were 18- to 29-year-olds (55 percent) and 50- to 64-year-olds (57 percent).

The latter demographic, DiCamillo said, “are people who grew up in the ’60s and early ’70s and they may be a little more tolerant to differences in lifestyles.”

Other findings in the poll were consistent with previous surveys on the issue, with Democrats overwhelmingly opposing the proposed ban and Republicans supporting it.

A majority of voters living in coastal areas oppose the ban, meanwhile, and a majority of those in inland counties generally support it.

The poll surveyed 672 likely California voters July 8-14. The margin of error is 3.9 percent.