Former president Barack Obama has privately told allies who have reached out to him that President Biden’s already-tough path to reelection grew more challenging after his shaky debate performance on Thursday — a harsher assessment of the presidential race than his public comments, according to several people familiar with his remarks.

Obama separately spoke directly with Biden by phone after last Thursday’s debate to offer his support as a sounding board and private counselor for his embattled former vice president, the people said, speaking on the condition of anonymity to discuss private conversations. It is unclear how directly Obama addressed Biden’s performance and his path to reelection on the call.

“President Biden is grateful for President Obama’s unwavering support since the very start of this campaign as both a powerful messenger to voters and a trusted adviser directly to the president,” Lauren Hitt, a spokeswoman for the Biden campaign, said in a statement. A spokesperson for Obama declined to comment.

Obama has long harbored worries about his party defeating Donald Trump in November, repeatedly warning Biden in recent months about how challenging it will be to win reelection. Just before the debate, Obama conveyed to allies his concerns about the state of the race.

As some Democrats call for Biden to drop out of the presidential race amid widespread panic, Obama has not voiced that conclusion. He sees his role as being helpful to Biden based on their history of working together, the people said. On Friday, Obama appeared at a fundraiser in New York for House Democrats, where he expressed continued support for Biden.

“Bad debate nights happen,” Obama wrote on social media after the debate. “Trust me, I know. But this election is still a choice between someone who has fought for ordinary folks his entire life and someone who only cares about himself. Between someone who tells the truth; who knows right from wrong and will give it to the American people straight — and someone who lies through his teeth for his own benefit. Last night didn’t change that, and it’s why so much is at stake in November.”

But for months, Obama has shared with Biden and friends his deep concerns about Trump’s political strengths and the real possibility he is reelected in November. In December, during a private lunch at the White House, Obama discussed the need for Biden to empower his campaign apparatus, suggesting he install a more senior level decision-maker at the Wilmington headquarters. The next month, Jennifer O’Malley Dillon and Mike Donilon left the White House to serve as campaign chair and chief strategist, respectively.

Last June, Obama outlined Trump’s political strengths during a private lunch with Biden, telling him that Trump benefited from an intensely loyal following, a Trump-friendly conservative media ecosystem and a deeply polarized country. During that lunch, Obama also promised to help Biden with his campaign.

Obama, the Democratic Party’s biggest star, has appeared at two major fundraisers with Biden in recent months. Last month, Biden and Obama headlined a Los Angeles fundraiser with George Clooney and Julia Roberts that raised more than $30 million. In April, Biden, Obama and former president Bill Clinton appeared together at Radio City Music Hall in New York City, raising more than $26 million.

Dan Balz contributed to this report.