Joe Biden and Barack Obama are getting the band back together Tuesday -- at least for the day, with the former president visiting his former vice president in the White House to try and restoke Democratic momentum ahead of midterm elections.

For Obama, it will be the first time he steps into the hallowed corridors and historic rooms since he left five years ago, handing power to Donald Trump and ushering in a period of political turmoil unprecedented in modern times.

For Biden, who served two terms as deputy to the first Black president before coming out of retirement to deny Trump a second term, this will also be a poignant moment.

Beset by aftershocks of the Covid-19 pandemic, galloping inflation, a bitterly obstructionist Republican opposition, and Russia's invasion of Ukraine, he's had more than a year to appreciate how hard the top job really is. His approval polls are dire, stuck in the low 40 percent range, with little sign of improvement.

The peg for the White House reunion is a relatively happy political event -- the 12th anniversary of the launch of the Affordable Care act, Obama's signature domestic achievement.

Popularly known as Obamacare, the subsidized healthcare plan expanded access to medical services to millions in a country where many are unable to afford to visit the doctor and dentist and risk being bankrupted by the cost of emergency operations.

"President Biden and former president Obama both see the Affordable Care Act is an example, a shining example, of how government can work for the American people," White House Press Secretary Jen Psaki said.

Republicans have made repeated, ferocious attempts to strip away a plan they denounce as socialism, but Obamacare has survived most assaults and under Biden seen expanded participation.

"Not only did it ensure that millions of people had access to affordable healthcare, but it has been an opportunity to build on that and make changes and make improvements over the course of time," Psaki said.

- Power lunch -

The real point of the Biden-Obama get-together is broader: a chance to reinforce Biden's centrist brand and reassure Democrats running scared ahead of what polls predict will be a crushing election defeat in November, with Republicans regaining control of Congress.

The White House set the mood music to chill, trying to erase any sense that Obama was coming on a rescue mission of any kind.

The two men will have lunch, "as they used to do on a weekly basis," Psaki said, adding that even if this is the first time Obama has been invited over, "they continue to talk regularly."

"They are real friends, not just Washington friends," she insisted.

Real friends are often said to be scarce in cutthroat Washington, but Barack and his wife Michelle Obama are certainly popular among Democrats and seen as able to sprinkle much needed magic dust on the party.

When it comes to the midterms, Obama is not exactly the best example: his Democrats were wiped out in the 2010 and 2014 congressional races.

On the other hand, Obama showed with his reelection in 2012 that a president can survive those earthquakes -- a lesson, perhaps, for Biden in 2024, when he may face a rerun of his battle against Trump.