Pomp, circumstance, a pope and politics will collide Thursday morning.

When Pope Francis speaks to the Congress in the House chamber, the faces of the two Catholics seated immediately behind him will tell the tale of his appeal.

(WATCH LIVE NOW : Pope Francis’ Address to Congress)

While their politics are very different, Vice President Joseph R. Biden Jr. and Speaker John A. Boehner are both known for wearing their hearts on their sleeves, and each will be tested by what the pope says.

And to ramp up the drama, the pope’s arrival comes as both men face critical decisions about their political future in the coming days.

When Francis talks about the sanctity of human life, it’ll put Biden and the Democrats in the room on the spot — with the nation days from a potential government shutdown fight over funding for Planned Parenthood.

For Boehner, who first invited the pope in March 2014, Francis talking about tackling climate change, immigration, income inequality and the Iran and Cuba deals could cause plenty of heartburn, if not waterworks from the famously emotional speaker.

But the visual impact of the pope’s political appeals will be lightened by protocol. The top party leaders have pressed their flocks not to cheer and stand at every point the pope makes in order to avoid the chamber devolving into a raucous and unseemly partisan competition.

That has the added advantage of covering up some nasty intraparty splits — notably among the Republicans on immigration, with Boehner talking repeatedly of the need for a legislative fix but the bulk of House Republicans running in the other direction and Donald Trump riding an anti-immigration wave to the top of the GOP presidential field.

It certainly would be uncomfortable for the Ohio Republican to stand and cheer a call for a compassionate immigration system if the bulk of his flock sits on their hands — or for Biden and Democrats to sit while Republicans cheer the pope on abortion and marriage.

Boehner is already facing what may be his most spirited revolt to date, with an attempt to dethrone him appearing likely to occur after a deal is reached to keep the government open next week — or to reopen it shortly thereafter, in what has become the sharpest legislative skirmish on abortion in years.

It’s expected Boehner will eventually rebuff his conservative wing’s calls to defund Planned Parenthood and provide for a “clean” CR in the face of the president’s veto vow and a Senate filibuster. But he will have to pass a tough test to get to that point while keeping his conference supportive of his continued leadership.

Boehner himself has shrugged off that challenge, and sounds pleased as punch about the papal visit.

“For a little Catholic boy like me, this is big stuff,” Boehner told the Cincinnati Enquirer Monday.

Boehner told the paper he’s looking forward to hearing whatever the pope has to say.

“I’ll digest just like anyone else will,” said Boehner, who will also meet privately with the pope.

Boehner also told his hometown paper he has worked to make this moment happen because he believes it will “help awaken the Congress and awaken the American people to our higher callings.”

For Biden, the occasion also could be a powerful, personal moment as he nears the make-or-break decision to run for president. Last week, Biden talked openly on “The Late Show with Stephen Colbert” with the Catholic talk-show host about his emotional struggle with the death of his son Beau.

Will the pope’s presence help a grieving father find the strength for one last run for the political brass ring?

In the broader congressional audience, this pope certainly has many admirers, particularly among Democrats who have been heartened by his increased emphasis on traditionally liberal priorities like the environment and poverty. Republicans are warier.

A church with social policies that generally aligns with the traditional values planks of the GOP on marriage, sex and abortion differs with them on economics, poverty and lately foreign affairs, and the new pontiff has tended to emphasize the latter, including in his speech at the White House Wednesday.

Climate change just might be the headline issue, even though the prospects of anything happening in Congress are approximately nil given many Republicans continue to express doubts about global warming even existing, let alone something that merits a legislative response.

On Wednesday, Francis said the climate issue can no longer be left to the next generation, and explicitly thanked the president for his efforts to combat air pollution.

Many lawmakers in both parties already heard that speech, of course, turning out along with 11,000 others on the South Lawn and tweeting out selfies and wonder at the spectacle.

But the reaction to that speech already showed pols sprinting to their corners, with Republicans, like Senate Majority Whip John Cornyn of Texas, talking about the sanctity of life and numerous Democrats talking about saving the planet.

“I want to hear more about what the WH calls the ‘shared values’ of POTUS and the Pope, especially when it come to the sanctity of human life,” Cornyn tweeted.

Expect more of the same.

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