"Occasionally he would invite me and the other counselor to join him in fasting on a weekday for a specific purpose," Bennett wrote in an e-mail. "For example, one purpose would be to seek inspiration regarding an important decision, another purpose would be to express love, support and solidarity to someone who was ill or going through very difficult times."

Whether Romney would maintain this observance from the nation's highest office, we can't know. But it looks like the White House kitchen staff may be in for a little downtime each month, if they're lucky.

Honoring the Sabbath, going to church and other Mormon observances

Sunday is a holy day for active LDS Church members. It's a time when Mormons attend their local congregation - it's known as a ward, which in Catholic-speak would be comparable to a parish - and worship with their families and community.

The ward closest to 1600 Pennsylvania Ave., and likely the one the Romneys would be assigned to, is the Washington D.C. 3rd Ward, which gathers in what Mormons call a "meetinghouse" or chapel on 16th Street NW. The Washington Post described this ward as consisting of mostly Democrats, half who are nonwhite (including plenty of Spanish speakers), and having openly gay members in its leadership.

Riess said while ward assignments are almost always determined geographically, sometimes there are exceptions. And the truth is there just isn't any precedent for how this would be handled for a U.S. president.

How much of his Sundays a President Romney could set aside for his faith is obviously uncertain. We already know he's been hard at work on the campaign trail, Sundays included -- though the senior aide we spoke to said he makes efforts to get to church when he can.

One need only look at President Jimmy Carter, who went so far as to teach Sunday school at his local Baptist church, to see how a sitting president can make room for faith, said Balmer of Dartmouth, who counts among his many books "God in the White House: How Faith Shaped the Presidency from John F. Kennedy to George W. Bush."

Romney faithfully showed up at church on Sundays while he was governor, unless an official function got in the way, Bennett said. And when Romney ran for U.S. Senate in 1994 against Ted Kennedy, Bennett -- then the ward's bishop -- assigned Romney to teach the weekly adult Sunday school class.

"He was in church virtually every Sunday teaching this class throughout the campaign, only occasionally arranging for a substitute teacher," his friend said.

Beyond church, Riess speculated about other observances Romney would uphold.

Mormons reserve Monday evenings for "family home evening," a time when families pray, study and sing together.

Someone serving in church leadership, who didn't want to be named because of the sensitivity of the subject matter, said he doubted the Romneys would observe family home evening since their kids are grown and gone. But Riess suspected that Romney and his wife, especially given the size of their brood -- five sons; 18 grandchildren -- and the likelihood that family would be passing through, would honor the Monday tradition in some way, even if it was just the two of them.

There's also a practice in LDS Church wards in which men who hold the priesthood -- which means the authority, for example, to perform baptisms and offer sacramental blessings -- are partnered up to visit other congregation members, ideally once a month, as home teachers.

The LDS Church does not have paid clergy, and this is one way that volunteer ward pastors, or the bishops, can make sure members get personal attention and lessons as needed.

So could home teachers come knocking on the White House doors?

It's possible, said Riess, though obviously there'd be background checks and no unannounced knockings.

But a U.S. president couldn't possibly be expected to regularly home teach others, right?

Probably not. But Romney did step up as governor, Bennett said.

"He both had home teachers, and he was assigned as a home teacher, when he was governor," Bennett said. "He and Ann would ensure they were available for their home teachers to visit, and he was faithful in doing his home teaching."

And then there's the big question: What about the temple?

Many non-Mormons falsely assume the large and often magnificent white LDS temples they see in their cities are where Latter-day Saints go for church. But Mormons gather for Sunday services in meetinghouses or chapels, which are usually plain, unimpressive structures.

The 140 temples currently in operation across the globe are actually closed on Sundays. Mormons view their temples as houses of the Lord, as Riess explained in her book, and they are not places for run-of-the-mill worship. Temples, instead, are reserved for the most sacred rituals -- the details of which are not to be discussed outside temple walls.

The temples are so sacred that the doors are not even open for all Mormons; only those deemed sufficiently worthy by local church leadership are granted a "temple recommend" or an entry card.

While sacred ceremonies or "ordinances" for the living -- such as weddings, during which couples are "sealed" for eternity -- happen inside, there are also rituals performed by living substitutes or proxies for those who have died. These rituals include baptisms, which have been at times a subject of controversy for the LDS Church.

Romney, who long served in church leadership, surely has a temple recommend. But does that mean he'd actually go to the Washington D.C. Temple, which sits about 10 miles north of the White House in Kensington, Maryland?

"If I were him, I'd probably just not go while I was president, if only out of courtesy to other patrons," said our source in church leadership who didn't want to be named. "It's not like it's some kind of 'go often or you'll go to hell' thing. It's just a standard part of being a committed Mormon, which you do if you can find the time."

And a President Romney couldn't go there, let alone anywhere else, without Secret Service. So if he wanted to go, would he be able to? Even Secret Service agents would be turned away from the temple without the right access card.

Not a problem, speculated Balmer of Dartmouth. He said finding qualified agents, if Romney hasn't found them already, would be easy.

It's well-known that the CIA, FBI and, by extension, he said he assumes, the Secret Service recruit at LDS Church-run Brigham Young University. All these agencies, Balmer said, are "looking for people who are good, loyal, patriotic Americans," and many Latter-day Saints, who believe in the divinity of the U.S. Constitution, fit that bill.

So if it would be important for Romney and the first lady to go to the temple, it should be possible.

And Riess said, given Romney's level of faith and church involvement over the years, she can't imagine that he wouldn't want to go. Minimally, she pointed out, there's bound to be a family member's wedding or "temple sealing" he'd want to attend.

"It would be a logistical problem," she said. "But I'm pretty sure they'd find a way."