The last time the Pope came to America - when Pope Benedict XVI visited in April 2008 - there were more Catholics, as a percentage of the population.
And while Catholics as a group now make up a slightly smaller part of the American population, the growing Hispanic population means that they are beginning to represent a larger percentage of Catholics in the U.S.
In 2007, the year before Benedict visited, 24 percent - or nearly one in every four Americans - called themselves Catholic. By last year, that percentage had dropped to a little over one in five - just 21 percent, according to the Pew Research Center.
The share of Catholics who are Hispanic has gone up five percentage points - their numbers are now over one-third of all Catholics in the U.S. That trend is likely to continue as the millennials grow up. In fact, of the nearly half of millennials who identify as Catholic, 46 percent are Hispanic, compared to the 43 percent who are white.
Catholicism used to be identified largely with the Northeast and Midwest - with European populations that had immigrated here in large numbers, especially in the 19th century.
But now, the Catholic population is shrinking in those regions and swelling in the South and West, where the growth is coming from Hispanic immigration. Now, some 27 percent of all Catholic adults in the United States were born abroad.
Politically, American Catholics are not necessarily a monolithic vote on issues. Pope Francis has found himself at odds with conservative Catholics - those who are more devout and likely to attend services more regularly. His views clash with this group on climate change, on his push to repair diplomatic relations between the U.S. and Cuba, as well as on addressing income inequality.
Catholic voters in the United States have in the most recent presidential election split their support, with 50 percent of Catholics supporting President Obama and 48 percent voting for Mitt Romney. In the 2008 election, the president's share was higher: he received 54 percent of the Catholic vote to John McCain's 45 percent.
But a closer look at the numbers shows that Mr. Obama saw a huge drop off in white Catholics between 2008 and 2012 - a seven percent loss of support. He picked up three quarters of the Hispanic Catholic vote, however, which helped offset his losses.
The Hispanic Catholic vote has become more heavily Democratic lately, rising from 65 percent who supported Al Gore in 2000 to the 75 percent that voted for Mr. Obama in 2012.
Gore won the Catholic vote by a scant three percentage points in 2000; George W. Bush won it by 5 percentage points four years later. Republicans have also won at least 50 percent of the white Catholic vote since 2000. Romney got 59 percent of their vote in 2012.
Jim Nicholson, a former ambassador to the Holy See and former chairman of the Republican National Committee, maintains Catholics have grown more conservative over the last 20 years.
"Their values about life and about marriage have aligned much more closely with the Republican Party than they have the Democrat Party and that's showing up in the polling places," he told CBS News. That may be true of the older white Catholics, but seems less true of the younger Hispanic Catholic voters, given their strong support for Mr. Obama.
A recent CBS News poll found that 63 percent of Catholics approve of the way Francis is handling social issues like abortion and same-sex marriage. Francis has been both critical of abortion and sympathetic to the moral questions women face.
He also announced earlier this year that it would be easier for women to receive absolution for the sin of abortion. He has also said that gay and lesbian people should not be marginalized because of their sexual orientation, but has stood staunch in his teaching that a marriage the union of one man and one woman.
Sen. Patrick Leahy, D-Vermont, said part of Francis' appeal is that his teachings are universal.
"[H]e reaches out to everybody and he makes it very clear that if you believe in humanity then you have to believe in all humanity not just those who look like you or share the same background you do," he told CBS News.
Leahy, himself a Catholic, also talked about the way that the Catholic roles in political life have changed since he was a student at Georgetown Law School and former President John F. Kennedy was running for president.
"There were rumors if he was elected the pope was going to move into the White House. You had television preachers who were so adamant against him," Leahy said. "Now we got a Catholic vice president. Nobody questions his religion. We have a Catholic speaker of the house - one of several we've had in both parties...since I've been in the senate. Nobody thinks anything about that."