The measure on the ballot was only 14 words long -- a simple statement that "only marriage between a man and a woman is valid or recognized in California."
But supporters of Proposition 8, in what political analysts said was an extremely effective strategy, made the race about much more than that.
They were able to focus the debate on their assertion that without the ban, public school children would be indoctrinated into accepting gay marriage against their parents' wishes, churches would be sanctioned for not performing same-sex weddings and the institution of marriage would be irreparably harmed.
Supporters of gay marriage, along with political leaders including Sen. Dianne Feinstein (D-San Francisco) and the state's superintendent of public instruction, denounced those messages as scare tactics, but they were not able to sway voters. Preliminary returns showed Proposition 8 passing 52% to 48%.
"It was masterful of the campaign to raise the implications of what it could mean in terms of the school system," said Republican political consultant Wayne Johnson. He said voters may have started out "thinking that as long as it doesn't affect me, do what you want" but the supporters shifted the focus to children.
In the wake of the vote, gay couples and their supporters mourned, held rallies, including one in West Hollywood on Wednesday night, filed legal challenges and, in some cases, rushed to the county recorder's office to tie the knot before the state stopped allowing it. The Los Angeles County registrar-recorder stopped issuing same-sex marriage licenses Wednesday afternoon.
At the West Hollywood rally, which drew thousands to San Vicente and Santa Monica boulevards Wednesday night, demonstrators vented their frustrations and cheered when passing cars honked in support. While officers were shutting down streets for the rally, a deputy was accidentally struck by a pickup and suffered minor injuries.
For many demonstrators who had backed Barack Obama for president, Tuesday's elections brought mixed emotions.
"I felt happy and then I felt crushed," said Chris Thurman, 24. He and another friend, 29-year-old T.J. Prokop, carried signs depicting separate straight drinking fountains and gay drinking fountains, a reference to the racially segregated South in the pre-Civil Rights era.
Demonstrator Chris Moll, 35, who was married in October and was carrying his 18-month-old daughter, Ella, in his arms, said the election did not alter his feelings about his marriage.
"Whatever happened last night does not change how I feel about my husband and my family," Moll said. "It is a tough feeling, but I know this is a strong community, and I know we'll find the next step."
Earlier Wednesday, Paul Waters of Valley Village summed up his feelings: "disappointment." "Straight couples don't have a way to be able to truly understand the depth of what this means." Waters married his partner of 15 years, Kevin Voecks, on June 17.
Like them, many gay-rights activists spent the day asking themselves how they had been defeated. At the polls Tuesday, voters throughout the state said proponents' argument about schools was a major part of the answer.
"I'm concerned about having to educate children," Sharon Smith said after she voted in Altadena.
Smith and other African American voters played a crucial role in the outcome. An exit poll of California voters showed that black voters sided in favor of the measure by margins of more than 2 to 1. Not only was the black vote weighted heavily in favor of Proposition 8, but black turnout -- spurred by Barack Obama's campaign for president -- was unusually large, making up roughly 10% of the voters. The exit poll was conducted by Edison Media Research and Mitofsky International for a consortium of news organizations.
The campaign against Proposition 8 also did relatively poorly in Los Angeles County, where voters were divided almost evenly. By contrast, on the other high-profile social issue on the ballot, Proposition 4 on abortion, the liberal side carried Los Angeles by a margin of almost 200,000 votes.
On Wednesday, the proposition's backers celebrated their victory.
"Marriage has been protected," said Cal Schell, 65, a resident of the Sacramento suburb of Rancho Cordova.
Schell said he felt sad that "there's a lot of people who have a lot of angst over this. But it is very important that this be protected. . . . Go to any country, any place in the world. Marriage between a man and a woman has been a part of our being clear back to the days of early time."
Ron Prentice of the Protect Marriage Coalition said in a statement that "the people of California stood up for traditional marriage and reclaimed this great institution. We are gratified that voters chose to protect traditional marriage and to enshrine its importance in the state Constitution."
The campaign against Proposition 8 refused to formally concede Wednesday, saying that there were too many provisional and mail-in ballots to be counted.