Pope Francis urged lawmakers at a joint meeting of Congress to balance concern for those living in poverty with protection from environmental deterioration, which he said was "caused by human activity." (AP)

Pope Francis, appearing Thursday before a bitterly partisan Congress, called for a unified “common responsibility” on issues that have vexed Washington and much of the world, challenging lawmakers to adopt a more open approach to global migration and combating climate change.

In a historic first address by a pope to Congress, the 78-year-old leader of the Roman Catholic Church said lawmakers had been called in the tradition of Moses to “keep alive their sense of unity by means of just legislation.”

“Politics is, instead, an expression of our compelling need to live as one, in order to build as one the greatest common good: that of a community which sacrifices particular interests in order to share, in justice and peace, its goods, its interests, its social life,” Francis said in a 50-minute speech before about 500 lawmakers and hundreds of their guests in the public gallery above.

The papal address had been one of the most eagerly anticipated events on this year’s political calendar, the result of a lengthy effort by House Speaker John A. Boehner (R-Ohio), whose Catholic upbringing has been a key part of his political image.

For Boehner and many other Catholic members of Congress, the pope’s visit was an emotional one. Boehner’s eyes moistened as he met the pontiff before his remarks, pointing out that he had worn a green tie, a color symbolizing hope in the Catholic tradition. Sen. Lisa Murkowski (R-Alaska) was speechless when the pope blessed two rosaries that she still grasped tightly in her hand long after his address.

What Pope Francis said, what Americans think

“He blessed me and I could not speak,” Murkowski said. “To have a special blessing is really quite extraordinary.”

Several former lawmakers returned to Washington to watch a simulcast of the pope’s speech in the Capitol’s Statuary Hall — and catch a post-speech glimpse of the pope when he came to that hall to pay his respects at a statue of Junípero Serra, whom Francis canonized Wednesday in the first such ceremony in the United States.

On the lawn outside the Capitol, the pope’s visit drew a crowd of the Catholic faithful and others who are simply fans of his positions.

Melinda Frank, 39, who is Episcopalian, traveled all day and night from Yukon, Alaska, to see Francis at the Capitol because she supports his message on environmental preservation, which she said is important for sustaining hunting and fishing in her home community.

“I’m an Alaskan native. We love this Pope,” she said. “He is for [fighting] climate change and indigenous rights.”

The pope, one of the most popular figures in the world, delivered his remarks to one of the nation’s most unpopular institutions, a Congress that for two decades has been marked by partisan feuds, particularly during President Obama’s seven-year tenure.

Pope Francis addresses a joint meeting of Congress urging lawmakers to take action on climate change, and sharing his views on the death penalty and immigration. (AP)

In recent years, Obama’s push for a broad plan to rewrite immigration laws — which includes a path to citizenship for millions of illegal immigrants — has been blocked by a Republican-led House. And in recent weeks, some House Republicans, outraged by controversial undercover videos of Planned Parenthood’s abortion-related activities, have threatened to shut down most of the federal government if the organization continues to receive about $500 million in taxpayer funding.

In something of a surprise, the pope steered clear of any direct mention of abortion rights, instead focusing on immigration, the global refu­gee crisis spurred by wars in the Middle East, the death penalty and global warming.

Although he was invited by a Republican speaker, the pope’s themes often challenged American conservative orthodoxy. One Republican — Rep. Paul A. Gosar (Ariz.) — announced that he would boycott the speech out of concern that Francis would drift into views on climate change that conservatives oppose.

The pontiff has advocated a more robust approach to combating climate change, and he made the most direct appeal of his speech to Congress to play its “important role” in averting “the most serious effects of the environmental deterioration caused by human activity.”

He also linked environmental conservation and preservation to the need to work for the greater social good elsewhere.

“We need a conversation which includes everyone, since the environmental challenge we are undergoing, and its human roots, concern and affect us all,” he said.

The papal address to the joint meeting of Congress stood in stark contrast to the speech delivered in the same House chamber in early March by Israeli Prime Minister Benjamin Netanyahu, whose staunch opposition to Obama’s pursuit of a nuclear deal with Iran turned the chamber into a collision of ideologies.

Francis, by contrast, devoted much of his speech to spiritual themes.

He cited the work of four Americans — President Abraham Lincoln and the Rev. Martin Luther King Jr., as well as Dorothy Day, a 20th-century social activist, and Thomas Merton, a Catholic monk — who he said embodied and “shaped fundamental values which will endure forever in the spirit of the American people.”

Francis cited his personal experience as a child of immigrants and said that the United States ought to adopt a more just approach to dealing with the immigrants at its door and in the country. “When the stranger in our midst appeals to us, we must not repeat the sins and the errors of the past,” he said.

He was even more resolute when calling for a more respectful attitude toward refugees who, he noted, are fleeing conflict in numbers not seen since World War II. Invoking the golden rule, the pope pressed Congress “to respond in a way which is always humane, just and fraternal” — and reminded them that, in time, how they treat others is how they, too, will be treated.

That moment, like many others in the speech, prompted Democrats to give a standing ovation, followed slowly by applause from Republicans. The pontiff did not ignore some conservative causes that Catholics believe in, but they were dressed in more subtle language.

Republicans rose to their feet at a reference that they assumed was the pope’s embrace of strict opposition to abortion: “The golden rule also reminds us of our responsibility to protect and defend human life at every stage of its development.”

However, many Democrats applauded loudly when he reminded the assembly that he firmly opposes the death penalty — and said he supports the work of bishops and activists trying to revive this national debate and move the prison system toward a culture of rehabilitation.

And in his call for peace in the world, the pope appeared to give a subtle nod to Obama and his team while making a less-subtle dig at the defense industry and those who espouse a military-first strategy. The pope challenged Congress to “stop the arms trade” of “deadly weapons being sold to those who plan to inflict untold suffering on individuals and society.” He criticized what he called “shameful and culpable silence,” and warned that those who sell weapons for money have innocent blood on their hands.

Without directly mentioning major diplomatic ventures such as the Iran deal or reopening ties with Cuba, Francis alluded to “efforts made in recent months” to help overcome deep differences and animosities.

“This has required, and requires, courage and daring, which is not the same as irresponsibility,” he said. “A good political leader is one who, with the interests of all in mind, seizes the moment in a spirit of openness and pragmatism.”

“Being at the service of dialogue and peace,” he added, “also means being truly determined to minimize and, in the long term, to end the many armed conflicts throughout our world.”

Ed O’Keefe, Kelsey Snell and Mike DeBonis contributed to this report.