San Francisco has long believed that it must be able to continue to destroy a magnificent valley in Yosemite National Park so it can have unrestricted access to water. And a new poll shows that the rest of California does not share that belief.

The poll shows that a plurality of California voters — 45.3 percent — say they would support legislation that would strip San Francisco of its Tuolumne River water rights unless Hetch Hetchy Valley in Yosemite National Park is restored by 2025. The poll showed that 38.4 percent of voters said they would oppose such a plan; 16.2 percent were undecided. A plurality of voters — 42.9 percent — also said they support a ballot measure initiative that would do the same thing.

The poll was commissioned by the environmental group Restore Hetch Hetchy, which wants the City of San Francisco to drain the massive O’Shaughnessy Dam in Yosemite so as to return the giant valley back to nature. The group has repeatedly noted that the city doesn’t need O’Shaughnessy, because San Francisco’s water supply actually comes from the Tuolumne, not the reservoir, and the city has other reservoirs in which to store water. The group sponsored a ballot measure in San Francisco last year that would have required the city to study the issue, but city residents voted overwhelmingly against it.

The rest of California, however, feels differently about Hetch Hetchy Valley. Under California law, the state cannot order the City of San Francisco to drain O’Shaughnessy Dam. But the state Legislature could effectively do it by threatening to strip San Francisco of its Tuolumne River water rights. And if the legislature was unwilling to pass such legislation, then California voters could do it through a statewide ballot measure.