Former President Barack Obama has intensified his efforts to support President Joe Biden's re-election campaign, making a recent visit to the White House for a strategy session and participating in a high-profile fundraiser alongside Biden and former President Bill Clinton. The increased involvement comes as Obama has expressed concerns to associates about the potential closeness of the upcoming election, emphasizing the need for an "all-hands-on-deck" approach, according to people familiar with his thinking.

During his visit to the White House last Friday, Obama spent several hours in the family dining room, engaging in a working meeting with Biden and key staff members. The two presidents, along with former House Speaker Nancy Pelosi, also participated in an organizing call commemorating the 14th anniversary of the Affordable Care Act. "We have the chance to do even more, but that only happens if we send Joe and Kamala back to the White House in November," Obama said during the call. "So, we've got to keep working."

Behind closed doors, Obama praised Biden's recent State of the Union address, noting its effectiveness and ability to break through to the public, according to sources familiar with their conversation. The former president also stressed the political potency and importance of healthcare as a key issue in the upcoming election.

Obama's most significant public embrace of Biden's re-election effort will take place on Thursday at a star-studded fundraiser in Manhattan, featuring both presidents alongside Clinton. The three leaders will engage in a rare conversation moderated by Stephen Colbert, highlighting the extraordinary moment in American history as Biden faces a bitter fight against his predecessor, Donald Trump.

"No one can speak to disillusioned Democrats better than President Obama," a senior strategist who has worked closely with both Obama and Biden told CNN, speaking on condition of anonymity. "But there are limits to what Obama can do. The burden to win this race is still on President Biden."

The sold-out event at Radio City Music Hall will attract numerous celebrities and artists, with tickets ranging from $225 to $500,000. Attendees will have the opportunity to have their photographs taken with all three presidents by renowned photographer Annie Leibovitz.

Since Biden's re-election announcement last year, Obama has been lending a hand through public fundraising appeals and private conversations aimed at allaying concerns from some Democrats about Biden seeking a second term. The campaign's grassroots fundraising efforts featuring the former president have raised over $15 million so far this cycle, with a "Meet the Presidents" contest featuring Biden and Obama alone bringing in $3 million.

Looking ahead, Obama plans to focus on motivating key voter demographics, particularly young Americans, Black, and Latino voters, who are seen as a potential weak spot for Biden's candidacy. The former president is expected to ramp up his efforts closer to the election, visiting college campuses and major cities in battleground states when his impact is believed to be most effective.

Obama's influence on domestic and foreign policy issues, such as the conflict in Gaza and reproductive rights, will also shape his message to voters. His unwavering commitment to helping Biden secure a second term reflects his belief in the importance and weight of the upcoming election.

"President Obama once said to me that every president is a reflection of the previous president, and he's right," said Jim Messina, Obama's 2012 campaign manager and a close adviser to the Biden re-election campaign. "Trump was the complete opposite of Obama, and Biden is the complete opposite of Trump. Being the president of the United States means you're part of a small club; there is no other group of people whose red flags about the direct threat of Donald Trump should be taken more seriously."