SAN FRANCISCO — Californians heeded warnings of legal chaos and other dangers and rejected a ballot measure Tuesday that would have made their state the first to legalize marijuana for recreational use.

The spirited campaign over Proposition 19 pitted the state’s political and law enforcement establishment against determined activists seeking to end the prohibition of pot.

It was by far the highest-profile of the 160 ballot measures being decided in 37 states. Other topics included abortion, tax cuts and health care reform.

On a night of conservative advances in much of the country, Massachusetts voters spurned a chance to cut their taxes — rejecting a proposal to lower the state sales tax from 6.25 percent to 3 percent. Critics said the cut would have forced the state to slash $2.5 billion in services, including local aid to cities and towns.

In Colorado, voters decisively defeated an anti-abortion “personhood” amendment — similar to one rejected in 2008 — that would have given unborn fetuses human rights in the state constitution.

California’s marijuana proposal would have allowed adults 21 and over to possess up to an ounce of pot, consume it in nonpublic places as long as no children were present, and grow it in small private plots. It would have authorized local governments to permit commercial pot cultivation, as well as the sale and use of marijuana at licensed establishments.

Proponents pitched it as a sensible, though unprecedented, experiment that would provide much-needed revenue for the cash-strapped state, dent the drug-related violence in Mexico by causing pot prices to plummet, and reduce marijuana arrests that they say disproportionately target minority youth.

However, every major newspaper, both political parties, the two candidates for governor and all but a handful of leading politicians came out against it.

“Today, Californians recognized that legalizing marijuana will not make our citizens healthier, solve California’s budget crisis, or reduce drug-related violence in Mexico,” said the White House drug czar, Gil Kerlikowske.

Instead, he said, legalization would lead to more addiction, driving accidents and emergency room admissions.

Federal officials also said they would have continued enforcing laws against marijuana possession and sales had the measure passed.

Prop 19 supporters blamed the outcome on the older, more conservative leanings of voters who participate in midterm elections and pledged to try again in two years.

“It’s still a historic moment in this very long struggle to end decades of failed marijuana prohibition,” said Stephen Gutwillig, California director for the Drug Policy Project. “Unquestionably, because of Proposition 19, marijuana legalization initiatives will be on the ballot in a number of states in 2012, and California is in the mix.”

Tim Rosales, who managed the No on 19 campaign, scoffed at that attitude from the losing side.

“If they think they are going to be back in two years, they must be smoking something,” he said. “This is a state that just bucked the national trend and went pretty hard on the Democratic side, but yet in the same vote opposed Prop 19. I think that says volumes as far as where California voters are on this issue.”

In South Dakota, voters rejected a measure to legalize medical marijuana — a step already taken by California and 13 other states. A medical marijuana measure also was on Arizona’s ballot, and Oregon voters were deciding whether to expand the state’s current medical marijuana law by authorizing state-licensed dispensaries.

Among other notable ballot issues on Tuesday:

—Arizona voters approved a measure banning affirmative action programs by state and local governments based on race, ethnicity or sex.

—Washington state’s voters repealed taxes on candy, soda and bottled water adopted by lawmakers last year — a move that could eliminate a projected $352 million in revenue over five years. Voters rejected a proposal to impose a state income tax on any income above $200,000, or $400,000 for couples.

—In the littlest state, voters chose to keep the longest formal name — opting to stay as Rhode Island and Providence Plantations, instead of just Rhode Island.

—In Illinois, where the two most recent former governors have been convicted on federal charges, voters approved an amendment that enable future governors to be recalled by popular vote.

—Oklahoma voters approved a proposed amendment aimed at nullifying the segment of the new federal health care law requiring people to have health insurance. Similar measures were on the ballots in Arizona and Colorado.

In Oklahoma, voters overwhelmingly passed three measures that had dismayed some progressive and immigrants-rights groups. One makes English the state’s “common and unifying language,” another requires a government-issued photo ID in order to vote, and the third prohibits state courts from considering international law or Islamic law when deciding cases.

—In Colorado, voters rejected three measures that would have banned borrowing for public works, cut the income tax and slashed school district property taxes. Opponents said the proposals would have cost the state $2.1 billion in revenue and eliminated tens of thousands of jobs.

—For the first time since the 1990s, there were no measures to ban same-sex marriage. But in Iowa, voters ousted three state Supreme Court justices who joined a unanimous 2009 ruling that legalized gay marriage there.