For President Biden, who is engaged in the fight of his political life, everything is politics these days, even going to church.
On Sunday morning, Mr. Biden spoke at a Black church service in Philadelphia, seeking to reassure the group of voters who helped him win the White House in 2020 that he is still capable of beating former President Donald J. Trump.
“The joy cometh in the morning,” Mr. Biden told several hundred people at Mount Airy Church of God in Christ, a political fixture in the city often visited by Democrats. “You’ve never given up in my life. And as your president, I’ve tried to walk my faith.”
Before Mr. Biden spoke, Rachel Hooks, a member of the church, offered a prayer that did not shy away from the doubts swirling around his candidacy.
“Touch his mind, O God, his body; rejuvenate him and his spirit, O God — bless him and give him direction,” Ms. Hooks said, echoing a similar plea for mental and physical strength she also offered for members of law enforcement.
During his speech, Mr. Biden spoke from notes, rather than from the teleprompter that usually guides his public addresses, and his remarks at points seemed jumbled and could be difficult to hear.
“I know I’m going to be inclined to go on longer than I should here,” the president said, before ending his speech after about seven minutes. The brevity was notable as he is under extreme scrutiny from the news media and the public for signs of physical or mental lapses.
But as he visited a supportive faith community in familiar territory, Mr. Biden, a lifelong Catholic, faced a political crisis unlike ever before.
A growing number of Democrats from across the party’s ideological spectrum are calling for him to drop out of the race over concerns about his age and mental sharpness. Some donors have grown skittish about pumping money into his re-election bid. Democratic operatives and elected officials worry that the Biden campaign’s main strategy — making the 2024 contest a referendum on Mr. Trump — has been turned on its head by the president’s poor debate performance.
Mr. Biden is holding firm, however. On Friday, he told ABC News that only the “Lord Almighty” could force him to step aside after delivering a defiant speech in Madison, Wis. That was an attitude that seemed to be shared by many congregants at the church service on Sunday.
“Let him know we’re with him, hallelujah,” one woman shouted out from the audience as Mr. Biden walked onstage and a choir sang.
Black voters make up a key segment of Mr. Biden’s coalition, although polls show their enthusiasm for his candidacy has dipped. Still, they have higher opinions of the president’s performance than other groups and are less likely to think he should drop out, according to a New York Times/Siena College survey conducted after the debate.
Mr. Biden is making efforts like Sunday’s visit to Philadelphia to rally their support. From the pulpit he talked about policies he has enacted that he said benefited Black Americans, highlighting his record on lowering the unemployment rate for Black workers, expanding health care access, passing gun reform through Congress and relieving some student debt.
Pennsylvania is one of the states that Mr. Biden almost certainly must win again if he hopes to retain the White House. And its largest city, Philadelphia, is one of his favorite places to campaign in. But Mr. Trump has pulled ahead in the state in many polls, and now leads the president by about three percentage points, according to a New York Times polling average.
Gov. Gavin Newsom of California, a top Biden surrogate, spent Friday and Saturday campaigning for the president in Western Pennsylvania and Bucks County, a hotly contested battleground. At the church, he was joined by Senator Bob Casey of Pennsylvania, a Democrat up for re-election, and Mayor Cherelle Parker of Philadelphia.
Mr. Biden had been expected to speak at a meeting of the National Education Association in Philadelphia on Sunday, but he pulled out last week after the powerful education union’s staff went on strike.
“President Biden is a fierce supporter of unions, and he won’t cross a picket line,” Lauren Hitt, a Biden campaign spokeswoman, said in a statement.
Instead, he turned to a Black congregation with ties to the civil rights movement, the type of community the president has turned to a number of times in his political career and one that has been a welcoming group of likely voters.
On Sunday afternoon, Mr. Biden will travel to Harrisburg for a community organizing event with union members.
Since he frequently lost his train of thought at the debate, Mr. Biden has largely stuck to delivering prepared remarks from a teleprompter. Without the device, he has sometimes struggled to speak clearly.
This week, he stumbled over his words during two radio interviews, even though his aides had provided the hosts with the questions, a practice that goes against standard journalistic ethics. And he gave several confusing answers during his interview with ABC News on Friday.
Even Mr. Biden’s allies have said that his campaign should ensure that he appears more in public without a teleprompter to demonstrate his mental sharpness.
“They don’t need scripted remarks,” said Steve Sisolak, the former Democratic governor of Nevada, who supports Mr. Biden. “He needs to show people that he can do it on the spot and answer questions — tough questions — and be out there with voters. Be out there, mingle with your folks.”
After the service, Mr. Biden met with congregants, shaking hands and snapping selfies for more than half an hour.
The president’s campaign will face a serious test this week when members of Congress return to Washington after the Fourth of July holiday. Their willingness to offer public support for Mr. Biden — or not — could determine whether he continues in the race.
Mr. Biden can only hope for a reception as friendly and optimistic as the one he got in Philadelphia on Sunday. Before the president spoke, he was introduced by an energetic sermon from Bishop J. Louis Felton.
“If Joseph can get out of the pit,” Mr. Felton preached, referencing an early biblical figure who was cast away by his brothers, “if Jesus can get out of the pit, then President Biden is coming back.”
