WASHINGTON (RNS) — When John Kerry, the White House’s special envoy on climate change, visited Pope Francis earlier this month, the moment garnered popular attention mostly for an image that emerged from the meeting: a pontiff known for appearing stone-faced in meetings with foreign leaders (not least former President Donald Trump) grasping Kerry’s outstretched hand, grinning from ear to ear.

According to Ken Hackett, former U.S. ambassador to the Vatican, the real surprise was that the meeting happened at all.

“That’s unique,” said Hackett, who served in Rome under President Barack Obama’s administration, from August 2013 to January 2017. “Generally, non-heads of state do not meet with the Holy Father for pragmatic reasons. The Holy Father can’t meet with every minister of the interior or foreign affairs from Tonga to Tanzania, you just can’t do it — there’s no time.”

Hackett guessed the visit with Kerry — who, despite numerous attempts, huddled with the pope only once during his tenure as secretary of state — had more to do with the policy than the person: Kerry was in Europe to discuss climate change, an issue Francis has made a focus of his papacy.

But even the context for the meeting contrasted sharply with the pope’s grumpy photo op with Trump in 2017, when Francis gave the then-president a copy of Laudato si’, his encyclical on climate change. If Trump read it, it didn’t take: A little more than a week later, he pulled the U.S. out of the Paris climate accords.

Even as President Joe Biden faces mounting pressure from U.S. Catholic bishops for his views on abortion, experts say the president’s policy positions on issues from immigration to poverty are likely to find resonance with the Vatican.

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Besides their common interests, said John Carr, director of the Initiative on Catholic Social Thought and Public Life at Georgetown University, Biden and Francis share many common experiences.

“You’ve got two older leaders at the end of their lives, who nobody really expected to be the pope and the president,” he said. “They’ve been underestimated, they’ve been dismissed, and both have institutions in crisis: The (U.S.) is going through COVID, a democratic crisis, a racial crisis; for the church: COVID and sex abuse.”

Perhaps more importantly, they share a healthy number of policy goals, including mutual interest in sub-topics like the overlap of environmentalism and economics.

“There are only a couple people who talk about climate change and work: Pope Francis and Joe Biden,” Carr explained, pointing to a section on workers in Laudato si’.

Seeking policy cooperation with the U.S. is the Vatican’s default posture, Hackett said. The verbal sparring that flared up between Francis and Trump, such as the pontiff’s suggestion in 2016 that then-candidate Trump was “not Christian” because of his proposed immigration policies, is far less common. (Trump retorted by calling the questioning of his faith “disgraceful.”) Francis later publicly criticized the administration’s policy of separating immigrant families along the U.S.-Mexico border.

“Yeah, that was different,” Hackett said, chuckling.

Anthea Butler, associate professor of religion at the University of Pennsylvania, suggested the contrast is rooted in more than just politics.

“The relationship that Joe Biden has with the pope is one that most Catholics would want to have with the Pope,” Butler said in an interview. “The relationship between Trump and the pope was adversarial, because there were so many things Trump did that were anathema to Christian teaching — and especially to Catholic church teaching — in terms of care for immigrants, among other things.”

The pope has shown a willingness to sidestep his American bishops to strengthen his relationship with Biden: On Inauguration Day, the U.S. Conference of Catholic Bishops issued a letter warning that Biden’s views on abortion “advance moral evils and threaten human life.” Francis, on the other hand, sent a letter congratulating him.

The Holy See has continued the trend since, appearing far less eager than the U.S. bishops to attack the second Catholic president in U.S. history: When USCCB leaders began discussing whether or not to withhold Communion from Catholic politicians who back abortion rights (which would include Biden), the Vatican’s theological watchdog sent the group a letter urging clerics to tap the brakes.

Butler said that the bishops’ “adversarial” posture toward Biden is more emblematic of domestic politics than the goals of the global Catholic Church.

“It shows their political leanings,” said Butler.

Most dialogue between the U.S. and the Holy See isn’t conducted by popes and presidents but through a bevy of diplomatic officials on both ends, with staffers regularly meeting to hash out policy points.

“The formal relationship happens between the State Department and the Holy See — that’s why you have an ambassador there,” Hackett said. “On a day-to-day basis, and sometimes an hour-to-hour basis, there are discussions and dialogue on a myriad of issues between the embassy and the Vatican at various levels — principally the (Holy See’s) secretariat of state, but not solely.”

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Biden, who keeps a picture behind his desk at the White House of himself meeting Francis, has yet to appoint an ambassador to the Vatican. Daily operations are currently overseen by the embassy’s chargé d’affaires, Patrick Connell. Hackett says embassy staffers were likely involved in a recent moment of synthesis between the Vatican and the White House: Biden’s decision to support loosening COVID-19 vaccine patents, a proposal the Vatican has backed for months.

The USCCB did not join other Catholic groups in lobbying the U.S. government on the patent issue — something Hackett explained is not atypical.

“On some issues, the Vatican just doesn’t go through the bishops’ conference,” he said. “On others, it does.”

The closer the relations between Washington and Rome, the more likely the pope is to become personally involved. Carr and Hackett both pointed to 2014, when Francis brokered the restoration of normalized relations between the U.S. and Cuba.

Carr joked: “Who could have thought that a Pope would come to the United States for the first time in his life through Havana?”

Both Butler and Hackett said they wouldn’t be surprised if Biden responded in kind to the pope’s friendly outreach by booking a visit to the Vatican himself.

“I would presume that Biden will be there shortly,” Hackett said.