As Tuesday's deadline to influence undecided voters on Proposition 8 – the ballot initiative that seeks to forbid gay marriage in California – nears, Christian fundamentalists are planning a twelve-hour prayer session in support of the gay marriage ban.

On Saturday, tens of thousands of people are expected to converge on San Diego's Qualcomm Stadium for a day-long event of praying and fasting in support of social conservative issues including gay marriage bans in California, Arizona and Florida and limits on abortion (Prop 4).

Focus on the Family Founder and Chairmam James Dobson revealed on Wednesday that he would participate in TheCall, as the event is known.

“It is not a festival, it is a fast,” Dobson told his radio listeners on Wednesday. “It's a day of concerted prayer from 10 o'clock in the morning till 10 o'clock at night.”

TheCall is the brainchild of former pastor Lou Engle, who organized the first Christian power-pray event in 2000, drawing 400,000 faithful to Washington D.C.

“This is a spiritual battle; it must be won in prayer,” Engle said in a conference call uniting 3,000 pastors to strategize against gay marriage in California. “We need to take away the rights of the powers of darkness to bring this kind of resolution forward.”

Rev. Jim Garlow, who has taken a leadership role in organizing the anti-gay marriage religious forces in California, asked Engle to come to San Diego and organize Saturday's event. Garlow, who currently heads the Skyline Wesleyan Church in La Mesa, California, also wrote to Dobson asking for his support.

Saturday's event is on the concluding day of a 40-day fast called for by Garlow in support of the gay marriage ban.

In the letter he wrote to Dobson, Garlow said the fight to rid California of gay marriage is an “epic battle for the sanctity of marriage.” He said that without the gay marriage ban, “marriage will never be the same.” Garlow has also linked gay marriage with the “destruction of Western civilization.”

On his radio program, Dobson said he was “deeply moved” by Garlow's appeal.

TheCall has drawn up to 400,000 evangelical Christian youth to various cities – Las Vegas, Dallas and Los Angeles included.

But while organizers describe the event as non-political – “We're not there to make a political statement,” said Engle – proponents of gay marriage say it's clearly an anti-gay political rally.

“Clearly the focus is on taking away this right [to gay marriage],” said Dale Kelly Bankhead, a No-On-8 spokeswoman. “It seems political to us.”

But worse, The Southern Poverty Law Center (SPLC), a group that tracks hate groups in America, has linked Engle to Joel's Army, a militant Christian fundamentalist group that advocates for the replacement of the American government with pro-Christian leaders that observe strict biblical laws.

James Dobson's attendance at the Saturday event is certain to increase its visibility and appeal among evangelical Christians. Dobson continues his reign as America's biggest advocate against gay and lesbian unions. His Christian broadcasting empire has donated millions to ban gay marriage in California, and his touring conference Love Won Out, which seeks to “cure” gay men and lesbian women from their gay identities, remains controversial.