Larsen, who sports a brown comb-over and tortoise shell glasses, arrived in Washington in the early 1980s as an intern for Hatch, also a Mormon.
He landed the internship courtesy of Brigham Young University, his alma mater. The Mormon school owns a four-story dorm on Pennsylvania Avenue, not too far from the White House, which houses 120 student interns each year. It's the school's largest such program in the nation.
"Part of our church's tradition is to be connected with civic life, to make our communities better," says BYU's Scott Dunaway, who helps place students on Capitol Hill, at the Smithsonian and other Washington institutions. "We don't believe in being reclusive."
It's a perfect characterization of Larsen. He grew up in Provo, in the shadow of BYU, and wanted to prove he could make it outside of Utah.
"Kids growing up in the LDS Church have been told, 'Go ye out in the world and preach the gospel of Christ - don't be afraid to be an example,' " Larsen said, sitting in the glass-doored conference room of the foundation he runs on K Street.
"So we are on our missions, converting people to Christianity," he continued. "And coming to Washington, for me and probably for a lot of people, came out of that interest. We see it as our career, but also we're going out to preach the word of Christ."
For Larsen, that usually means correcting misinformation about Mormonism or explaining Mormon beliefs and practices -- you really don't drink coffee, ever? -- over lunch with co-workers or at business functions, rather than on-the-job proselytizing.
He learned about integrating work and faith from Hatch. He was initially shocked to discover that the senator prays in his office each morning. Larsen and Hatch developed what the bishop calls a "father-son" relationship, with the intern rising up through the ranks to become Hatch's chief Washington fundraiser.
"We would go on trips, and I'd quiz him on the plane: Why did the church do this? Why didn't the church do this?" Larsen said. "He was like a tutor to me."
Now, as the head of a foundation that educates teachers about the U.S. Constitution, the bishop helps other young Mormons with job leads and introductions. Larsen was appointed to the role by Hatch and the late U.S. Sen. Ted Kennedy.
Much of Washington's Mormon professional network is still anchored by BYU, which operates a handful of big, well-connected alumni groups with major Washington chapters. The most prominent is BYU's Management Society, a global organization whose biggest chapter is in Washington.
At the chapter's recent alumni dinner, former Secretary of State Condoleezza Rice was the guest of honor. She has strong ties to the Mormon community and has hired Mormons as top aides. Says Larsen: "Condi's got a ton of Mormon contacts."
Patrice Pederson also knows how to work a Rolodex. A lifelong political activist, she moved from Utah to Washington last year and soon tapped into BYU's local network.
Pederson served as the U.S.-based campaign manager for Yeah Samake, a Mormon running for president in the West African nation of Mali.
Samake traveled frequently to the U.S. to raise money and build political support, so Pederson enlisted the help of BYU's Management Society and other groups to host events for the candidate.
Both in Washington and across the U.S., many Mormons are watching his candidacy.
"Members of the church on Capital Hill were anxious to introduce the candidate to other members of Congress," says Pederson, sipping an herbal tea (Mormons eschew black leaf teas) in a strip mall Starbucks near her apartment in Alexandria, Virginia.
"It's cool to have a member of the church running for president in Africa."
Beyond making connections, many Washington Mormons say the LDS Church provides an ideal proving ground for careers here.
Unlike most churches, it has no professional clergy; from the bishop to the organist, each role is filled by everyday Mormons, most of whom have other day jobs. As a result, Mormons take church leadership roles at an early age, speaking publicly at Sunday services almost as soon they learn to talk.
"My kids grew up in the church, and we get together for three hours on Sundays, and each member needs to get up and speak," says U.S. Rep. Jason Chaffetz, R-Utah. "By the time they graduate, they have all these speaking assignments that other teenagers just don't have.
"For those who grow up in the Mormon church, they are taught skills that allow them to be successful in a tough city like Washington," says Chaffetz, who converted to Mormonism shortly after college.
Young Mormons also hone leadership skills by serving missions away from home. The missions last from one and half to two years and happen when Mormons are in their late teens and early 20s and often include intensive foreign language training.
"Young Mormons are more formidable in public settings and international settings than others," says Terryl Givens, a Mormon scholar at the University of Richmond. "Normally you would have to acquire more age and work experience before you feel comfortable and useful at NGOs and think tanks."
Chaffetz, whose son is serving a mission in Ghana, says the experience is the perfect preparation for political careers.