The torrent of money that poured into campaigns for and against California's Proposition 8 may make it the costliest state ballot measure ever.

Contributions to both sides of the successful ballot measure to ban same-sex marriage have already topped a total of $75.2 million, according to disclosures filed with the California secretary of state. And almost 5 cents of every dollar came from Utah.

The picture may change when full financial reports are filed in late January, but documents now show Proposition 8's unsuccessful opponents actually out-raised supporters by about $1.9 million, yet still lost by 504,853 votes, a 4 percent margin.

''It was the most expensive social issue on a ballot anywhere,'' said Fred Schubert, a spokesman for ProtectMarriage.com, by far the biggest official fundraising group in favor of Proposition 8.

''I believe it simply reflects the passions people have surrounding the issue of marriage, on both sides,'' he said.

Those passions ran deep for Utahns, judging from the $3.6 million state residents contributed to the California campaigns. Fully 70 percent of Utah donations, or $2.58 million, went in support of the same-sex marriage ban, while $1.1 million was given to oppose it.

Utah ranked second only to California itself for total donations in support, while it ranked sixth for opposing donations, behind California and such heavily populated states as New York, Ohio, Illinois and Michigan.

Utah's big-dollar involvement can be linked to the LDS Church, the state's dominant institution, which urged churchgoers in a variety of ways to support the measure with their time and money. While Catholic and Evangelical churches and affiliated groups gave cash directly to support Prop 8, official Mormon involvement centered on nonmonetary and organizational aid, in addition to rallying church members, documents show.

''Mormon members were instrumental in the campaign, there's no question,'' Schubert said from his Sacramento office. ''They donated far in excess of their representation in the population.''

Utah's numbers also were pushed dramatically skyward by a public-giving duel between former Word Perfect executives Bruce Bastian and Alan Ashton, estranged friends on opposite sides of the issue who each threw $1 million into the fray.

Bastian, of Orem, is gay and has given to similar causes in the past. Ashton, a Lindon resident, is an active member of the LDS Church, former mission president and grandson of the late LDS Church President David O. McKay. After initially giving $5,000 to the anti-Prop 8 Human Rights Campaign in May, Bastian gave $1 million in July. Ashton countered with a $1 million donation to ProtectMarriage.com in October.

''I gave my money because I was fearful, when the church stepped in, of what would happen, and it happened,'' Bastian said. ''And I think other people like me were trying to counter what they saw the church doing.''

Bastian said Prop 8 and the LDS Church's involvement had pitted family members, churchgoers and work colleagues against one another across the country. ''There is a lot of anger and hurt and it's not going away.''

Ashton did not return calls seeking comment.

At least 720 Utahns donated to the Prop 8 battle between Jan. 1 and Election Day, reports show, with about 78 percent of them supporting Prop 8. Utah donors on both sides work from a diverse range of jobs, from software millionaires, engineers and attorneys to ranchers, housewives, retirees and self-employed filmmakers.

While the majority of Utah donors did not list their employer on California financial disclosures, the top employers among those who did were Brigham Young University, the LDS Church and the University of Utah.

Donations came from residents in 80 different Utah cities and towns, spanning 16 of Utah's 29 counties. Opponents tended to live in Utah's 26 largest cities, while supporters were spread among 76 communities, large and small.

A majority of Utah contributors to the opposing side came from Salt Lake City. Supporters were more widely dispersed around the state, with concentrations in Provo, Salt Lake City, Orem, Bountiful, St. George and Sandy.

Excluding the Bastian-Ashton donations, the average donation by Utah supporters was $2,792, while opponents averaged $440 apiece.

Opponents of Prop 8 have been combing through donation reports since their defeat, seeking in some cases to publicize and target big-ticket supporters with calls of business boycotts. Several Utah donors contacted by The Salt Lake Tribune refused to comment, citing fear of retaliation. One rural Utah business owner who made a five-figure donation in supporting the measure said he had received harassing calls.

Another donor, Janna Morrell, a homemaker from Providence, gave $15,000 to ProtectMarriage.com in the closing days of the campaign. Later, when one California-based anti-Prop 8 group began posting names of large contributors on its Web site, instead of worrying, the 42-year-old mother of 12 called to insist they include her.

''I'm going to stand up even in the face of danger,'' said Morrell, who is LDS and learned about the measure from her brother, a California resident active in the campaign. ''I believe strongly that Proposition 8 is not meant to be anti-gay but it is meant to be in favor of marriage.''

tsemerad@sltrib.com