"Every generation has a moment where they have had to stand up for democracy. To stand up for their fundamental freedoms," Biden wrote on Twitter, along with a video.
"I believe this is ours. That's why I'm running for re-election as president of the United States. Join us. Let's finish the job."
Biden has no real challenger from within the Democratic Party. However, Biden's approval ratings have not topped 50 percent for more than a year and a half.
However, he has consistently over-delivered when it matters. Supporters say the Democratic Party's surprisingly strong performance in 2022 midterm congressional elections validated the Biden brand.
But in a campaign that may result in a rematch of the 2020 election against Donald Trump, he is expected to face constant and fierce scrutiny over his age.
The veteran Democrat would be 86 by the end of a second term. Even if a medical exam in February found him "fit" to execute the duties of the presidency, many including in his own voter base believe he is too old.
An NBC News poll released over the weekend found that 70 percent of Americans, including 51 percent of Democrats, believe he should not run.
Biden likes to answer those concerns by saying, "watch me" - meaning that voters should focus on his policy wins at home and his marshaling of an unprecedented Western alliance to help Ukraine defend itself against Russia's invasion.
Over the next year and a half, Biden will have all the advantages of incumbency, backed by a united party, while Republicans are only just starting a messy primary season.
Trump, despite becoming the first former or serving president to be criminally indicted - and facing probes into his attempt to overturn his loss to Biden in the 2020 election - is the overwhelming Republican frontrunner.
And while Biden may seem bland in comparison to Trump, he would bank on his moderate, old fashioned image being the secret weapon needed in an increasingly extreme era.
"My dad had an expression," Biden often says. "'Joey, don't compare me to the Almighty. Compare me to the alternative.'"