Voters in Colorado and South Dakota rejected ballot measures yesterday that could have led to sweeping bans of abortion, and Washington became only the second state --after Oregon -- to offer terminally ill people the option of physician-assisted suicide.

In California, exit polls suggested a close race on a high-profile measure that would ban gay marriage -- the first time such a vote has taken place in state where such unions are legal. Three other states seemed headed toward enacting measures that would curtail the rights of same-sex couples.

For the abortion rights movement, it was a day of relief and celebration.

The Colorado measure, which was defeated soundly, would have defined life as beginning at conception. Its opponents said it could lead to the outlawing of some types of birth control as well as abortion.

The South Dakota measure would have banned abortions except in cases of rape, incest and serious health threat to the mother. A tougher version, without the rape and incest exceptions, lost in 2006. Anti-abortion activists thought the modifications would win approval, but the margin of defeat was similar, about 55 percent to 45 percent of the vote.

Elsewhere, the marijuana reform movement won two prized victories, with Massachusetts voters decriminalizing possession of small amounts of the drug and Michigan joining 12 other states in allowing use of pot for medical purposes.

Henceforth, people caught in Massachusetts with an ounce or less of pot will no longer face criminal penalties. Instead, they'll forfeit the marijuana and pay a $100 civil fine. Barnstable District Attorney Michael O'Keefe, who led opposition to the measure, called it "bad public policy."

The Michigan measure will allow severely ill patients to register with the state and legally buy, grow and use small amounts of marijuana to relieve pain, nausea, appetite loss and other symptoms.

Of the 153 measures at stake nationwide, the most momentous was the proposed constitutional amendment in California that would limit marriage to heterosexual couples.

Similar measures had prevailed in 27 states before yesterday's elections, but none were in California's situation -- with thousands of gay couples already married after a state Supreme Court ruling in May.

The opposing sides together raised about $70 million, much of it from out of state, to wage their campaigns. The outcome, either way, will have a huge impact on prospects for spreading same-sex marriage to the 47 states that do not allow it.

Though Democrat Barack Obama won the presidential race in California on his way to wrapping up his White House bid, the vote on the same-sex marriage amendment was expected to be close. A crucial question was how churchgoing black and Hispanic voters - presumably a pro-Obama constituency - would vote on the ballot measure.

According to exit polls, blacks were far more likely than whites or Hispanics to support the ban. Age also was a key factor - the exit polls showed voters under 30 opposing the ban by a 2-to-1 ratio, while most voters 60 and older supported the ban.

Obama opposed the California amendment and endorses the concept of broader rights for same-sex couples.

A ban-gay-marriage amendment was approved in Arizona; a similar measure appeared headed for passage in Florida.

Gay rights forces also suffered a loss in Arkansas, where voters approved a measure banning unmarried couples from serving as adoptive or foster parents. Supporters made clear that gays and lesbians were their main target.

Nebraska voters, meanwhile, approved a ban on race- and gender-based affirmative action, similar to measures previously approved in California, Michigan and Washington. Returns in Colorado on a similar measure were too close to call.

Gambling was on the ballot in several states. Arkansas voters approved a measure creating a statewide lottery, overturning a ban dating to 1874.

In Ohio, voters once again rejected a proposal to open the state's first casino. They also approved a new payday-lending law that cut the annual percentage rate that lenders can charge to 28 percent and limits the number of loans customers can take to four per year. Ohio's is now among the strictest laws in the country.