I don't understand the surprise that Obama voters would vote in favor of Proposition 8. Obama is against gay marriage so why would it be a surprise that many of his supporters are as well?
From Wikipedia:
"Equality for All was the lead organization opposed to Proposition 8.[72] They also ran the NoOnProp8.com campaign.[73] The nonpartisan League of Women Voters of California opposes Proposition 8 because "no person or group should suffer legal, economic or administrative discrimination."[74]
Republican California Governor Arnold Schwarzenegger stated that although he opposed and twice vetoed legislative bills that would recognize same sex marriage in California,
he respects and will uphold the court's ruling and opposes the initiative and other attempts to amend the state's constitution.[75][76] While a Democratic presidential nominee and
U.S. Senator, Barack Obama stated that he personally considers marriage to be between a man and woman,[77] and supports civil unions that confer comparable rights rather than gay marriage,[78] he stated
that he opposed the proposition and other attempts to amend the federal and state constitutions.[79][80] Democratic vice-presidential candidate Joseph Biden opposed the proposition.[81] The U.S. House Speaker, California Representative (8th District), Nancy Pelosi[82] along with twenty other members of the 53 member California congressional delegation and both of California's U.S. senators, Dianne Feinstein and Barbara Boxer, voiced their opposition to Proposition 8,[83] as did the Lieutenant Governor, State Controller, 42 of 80 members of the state assembly, 20 of the 40 state senators and the mayors of San Francisco, Los Angeles, and San Diego: Gavin Newsom, Antonio Villaraigosa, and Jerry Sanders respectively.[84][85][86][87]
San Francisco Mayor Gavin Newsom speaks at an Anti-Proposition 8 Rally at Sproul Plaza.All ten of the state's largest newspapers editorialized against Proposition 8: the Los Angeles Times,[88] the San Francisco Chronicle,[89] the San Diego Union-Tribune,[90] The Orange County Register,[91] The Sacramento Bee,[92] the San Jose Mercury News,[93] the Contra Costa Times,[94] The Press-Enterprise (Riverside-San Bernardino),[95] The Fresno Bee,[96] and the Daily News (Los Angeles).[97] Other papers to have editorialized in opposition include The New York Times,[98] La Opinión (Los Angeles), [99] and The Bakersfield Californian.[100]
A coalition of Silicon Valley executives urged a 'No' vote on Proposition 8.[101] Google officially opposed Proposition 8 "as an issue of equality."[102] Apple Inc. also opposed Proposition 8 as a "fundamental" civil rights issue, and donated $100,000 to the No on 8 campaign.[103][104] Biotech leaders warned of potential damage to the state's $73 billion industry, citing Massachusetts as a top competitor for employees.[105]
All six Episcopal diocesan bishops in California jointly issued a statement opposing Proposition 8 on September 10, 2008.[106] Southern California's largest collection of rabbis, the Board of Rabbis of Southern California, voted to oppose Proposition 8.[107] Other Jewish groups who opposed Proposition 8 include Jewish Mosaic,[108] the American Jewish Committee, Progressive Jewish Alliance, National Council of Jewish Women, and the Anti-Defamation League.[56][109]
The Los Angeles Unified School District Board of Education voted unanimously for a resolution to oppose Proposition 8.[110] The California Teachers Association donated one million dollars to fight Proposition 8.[111] Chancellor Robert Birgeneau of UC Berkeley urged a vote against the measure, citing the "likely" threat to California's academic competitiveness if Proposition 8 is passed.[112]
In general the entertainment industry was opposed to Proposition 8.[113]"