But the trip gave Sanders a moment on the world stage, placing him alongside priests, bishops, academics and two South American presidents.
Sanders has been at a disadvantage during his campaign against Clinton, President Barack Obama's former secretary of state, on issues of foreign policy, but he was peppered with questions from academics and ecclesiastics in a manner that might have been afforded a head of state.
Sanders trails Clinton in the Democratic primaries, but the trip to the Vatican and his massive rally earlier this week with 27,000 people in New York City may have offered a glimpse of the senator's aim to become a progressive leader - win or lose.
The discussions gave him a chance to expand on his core campaign messages about the need to reform banking regulations, campaign finance rules, and higher education. Asked about inequality in public education, he said it was "beyond disgraceful" and cited challenging conditions in Detroit's school system.
He told the audience that rather than a world economy that looks out for the common good, "we have been left with an economy operated for the top 1 percent, who get richer and richer as the working class, the young and the poor fall further and further behind".
