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Brandon Wade, Associated Press
Republican presidential candidate Rick Santorum speaks to attendees during a North Texas Presidential Forum hosted by Faith & Freedom Coalition and Prestonwood Baptist Church, Sunday, Oct. 18, 2015, in Plano, Texas. Six Republican presidential candidates converged on the church in suburban Dallas on Sunday, underscoring how important the evangelical vote is to many White House hopefuls.

PLANO, Texas — Six Republican presidential candidates made personal appeals Sunday to thousands of Christian conservatives at a megachurch in suburban Dallas, underscoring the importance of the evangelical vote.

It also emphasized the outsized role Texas' earlier-than-usual primary could play in the 2016 race.

Tea party and home-state favorite Sen. Ted Cruz, retired neurosurgeon Ben Carson, former Arkansas Gov. Mike Huckabee and former Pennsylvania Sen. Rick Santorum were speaking during a four-hour forum at the Prestonwood Baptist Church in Plano which organizers said was attended by at least 7,000 people.

Cruz, Huckabee and Santorum already enjoy strong support from churchgoers, as does Carson, whose unorthodox campaign has been buoyed for years by religious conservatives.

Prestonwood claims nearly 40,000 members over three Dallas-area campuses. Also appearing were Former Florida Gov. Jeb Bush and former Hewlett-Packard CEO Carly Fiorina, both of whom would like to boost their appeal to evangelical Republicans. Front-runner Donald Trump didn't attend.

"Everyone was invited to come but we believe the right people are in the room today," said pastor Jack Graham, who interviewed all the candidates about the importance of faith in their lives. He identified those gathered as evangelicals whom he called "Christians who believe the Bible." Santorum subsequently declared himself an "evangelical Catholic."

Cruz said faith in America "was under assault," prompting some in the sprawling, stadium-style sanctuary to bellow "Yes!" He pointed to the Supreme Court ruling legalizing gay marriage, and to businesses that he said had faced boycotts because they opposed same-sex weddings on religious grounds.

"I believe that 2016 is going to be a religious-liberty election," Cruz said to raucous applause. "As these threats grow darker and darker and darker, they are waking people up here in Texas and all across this country."

Fiorina was more subdued, saying her faith was once "a little abstract" since "I came to think of God as a CEO of a big enterprise. He was in charge, but he couldn't possibly know every little detail."

But, she told the faithful, she later discovered that "each one of us can have a personal relationship with Jesus Christ."

"God knows what's going on in our lives," she said, "and that personal relationship saw me through many hard times."

A devout Roman Catholic, Bush strengthened his defense-of-life bona fides while governor. He intervened in the case of Terri Schiavo, a brain-damaged Florida woman at the center of a protracted court fight over having her feeding tube removed.

Grassroots groups in tea party-dominated Texas largely have shunned Bush in favor of insurgent candidates like Cruz or Trump, but Bush has courted Christian conservatives at many events around the country organized by the Faith and Freedom Coalition, which also helped put together Sunday's gathering.

The Plano forum also offers presidential hopefuls a chance to make inroads in Texas, the country's largest conservative state. Officials moved the presidential primary up from May to March 1, and Texas is now set to be the largest of 13 states voting on "Super Tuesday."

Former Gov. Rick Perry has already abandoned his short-lived 2016 presidential bid, but Cruz, who lives in Houston, has spent relatively little time in Texas as he campaigns across the country.

Bush was born in the oil-patch town of Midland, and his son George P. Bush was elected Texas land commissioner last year. But the former governor has done more fundraising than campaigning in the state thus far.