It was a personal moment, one of only a few seen so far from a candidate who favors a tightly controlled campaign operation, and who, while attending church most Sundays, always does so out of sight of his accompanying media entourage.

It also reflected the changing dynamic of the GOP campaign.

According to exit and entrance polls for The Associated Press and television networks, former Arkansas Gov. Mike Huckabee's initial win in the Iowa caucuses was fueled by the 60 percent of GOP voters who called themselves born-again or evangelical Christians.

Many of them have been taught that Mormonism is a "cult" and not a Christian faith. They flocked to Huckabee, once a Southern Baptist minister.

Yet their dominance has dissipated.

In subsequent contests in New Hampshire, where Romney again finished second, and Michigan, where he won, the number of evangelical voters was far fewer, and Huckabee shared their support with his opponents. And while Huckabee did about as well in South Carolina as he'd done in Iowa with evangelicals, it wasn't enough to overcome Huckabee's weak performance with other voters.

Romney and his closest competitor for the nomination, Arizona Sen. John McCain, have both done better among non-evangelical voters than with evangelicals, and with those saying it is not important they share religious beliefs with their candidate than with those who say that is important.

Still, there are concerns about a Mormon president among some Republicans.

An AP-Yahoo News poll shows that Romney has had very little success gaining the support of Republicans who have long-standing reservations about the idea of voting for a Mormon candidate. That group of Republicans represents half the party, and Romney trails McCain and Huckabee by 20 points each with those voters. Romney has made some gains with the other half of the party who felt more comfortable with the idea of voting for a Mormon, and now leads McCain among them.

That is not to say Mormons have not been an active force behind Romney's campaign.

Numerous church members are volunteering on his staff, busloads traveled from southern California and Utah to Nevada before the latter state's caucuses, and their impact is expected to be especially important in the 21 GOP contests on Tuesday, when large Mormon populations go to vote in Arizona, California and Utah — all among the current top targets for Romney's campaign.

Their strength in the West was evident in Romney's Nevada win: He got 95 percent of the votes of Mormons, in a contest where they comprised 25 percent of the overall turnout.

Romney's attendance at Hinckley's service will give further exposure to their shared faith, but many of those who tune in may be surprised by how similar things look to funeral rites they've witnessed in their own faith.

The service will be held not in a ward house, but at the church's Conference Center in Salt Lake City. The venue was chosen for its ability to handle a crowd expected to number 21,000, just as St. Peter's Square would accommodate the overflow crowd for a papal service.

Hinckley will be buried in traditional all-white Mormon funeral clothes, but the rest of the service will be conducted by officials dressed in the same business suits seen on Easter or Christmas in Christian houses of worship.

And there will be eulogy-like tributes from family members and friends, as well as singing.

The music will be performed by the Mormon Tabernacle Choir — the church symbol that to date has been the most recognized and embraced by outsiders.