US President Joe Biden has officially announced his bid for re-election, asking Americans to help him "finish the job" he started more than two years ago.

Mr Biden, 80, faced a turbulent first two years in office marked by the Covid-19 pandemic, economic woes and geopolitical challenges including the US pull-out from Afghanistan and Russia's invasion of Ukraine.

On the campaign trail, Mr Biden - who served as Vice-President under Barack Obama - is likely to focus on his efforts to prop up the US economy after the pandemic, as well as his successes pushing through legislation focused on infrastructure, climate change and prescription drugs.

But a key argument for a second term will be what he has described as a turn towards authoritarianism from Donald Trump and his supporters in the "Make America Great Again" movement.

"The question we are facing is whether in the years ahead we have more freedom or less freedom, more rights or fewer," he said in a video launching his new campaign. "I know what I want the answer to be. This is not a time to be complacent. That's why I'm running for re-election."

The President, however, is also likely to face questions about his age and ability to serve, as well as about his handling of inflation, immigration and other issues that worry Americans.

The upcoming campaign is likely the last in a career in politics that has spanned more than four decades, and may again see him square off against Donald Trump.

So who is Joe Biden and how did he get to the White House?

Mr Biden ran for the Democratic 2008 nomination before dropping out and joining the Obama ticket.

His eight years in the Obama White House - where he frequently appeared at the president's side - has allowed Mr Biden to lay claim to much of Mr Obama's legacy, including passage of the Affordable Care Act, as well as the stimulus package and reforms enacted in response to the financial crisis.

As a long-time Washington insider, Mr Biden had solid foreign affairs credentials, and helped balance Mr Obama's comparative lack of executive experience.

The so-called "Middle Class Joe" was also brought on board to help woo the blue-collar white voters who had proved a difficult group for Mr Obama to win over.

He made headlines in 2012 by saying he was "absolutely comfortable" with same-sex marriage, comments that were seen to undercut the president, who had yet to give full-throated support for the policy. Mr Obama ultimately did so, just days after Mr Biden.

Mr Biden's two terms supporting the first black president followed a long political career.

The six-term senator from Delaware was first elected in 1972. He ran for president in 1988 but withdrew after he admitted to plagiarising a speech by the then leader of the British Labour Party, Neil Kinnock.

His lengthy tenure in the nation's capital has given critics ample material for attacks.

Early in his career, he sided with southern segregationists in opposing court-ordered school bussing to racially integrate public schools.

And, as chair of the Senate Judiciary Committee in 1991, he oversaw Clarence Thomas's Supreme Court confirmation hearings and has been sharply criticised for his handling of Anita Hill's allegations that she was sexually harassed by the nominee.

Mr Biden was also a fierce advocate of a 1994 anti-crime bill that many on the left now say encouraged lengthy sentences and mass incarceration.

The record made Mr Obama's moderate vice-president a sometimes uncomfortable fit for the modern Democratic Party.

Mr Biden's life has been dogged by personal tragedy.

In 1972, shortly after he won his first Senate race, he lost his first wife, Neilia, and baby daughter, Naomi, in a car accident. He famously took the oath of office for his first Senate term from the hospital room of his toddler sons Beau and Hunter, who both survived the accident.

In 2015, Beau died of brain cancer at the age of 46. The younger Biden was seen as a rising star of US politics and had intended to run for Delaware state governor in 2016.

Mr Biden garnered considerable goodwill following Beau's death, which served to highlight one of Mr Biden's central strengths: a reputation as a kind and relatable family man.

This perceived warmth is not without its pitfalls. After entering the 2020 race, he faced accusations of unwelcome physical contact during interactions with female voters - complete with uncomfortable accompanying footage.

But the avuncular politician responded by saying he was an empathetic person, though he accepted standards had changed. The episode, however, stoked a perception for some that he was out of touch.

Mr Biden's return to the White House came at a difficult time in US politics, with the country still reeling from the Covid-19 pandemic.

Just two weeks before his inauguration, the country had also seen supporters of former President Donald Trump storm Congress in a bid to thwart the certification of his election victory after Mr Trump falsely claimed that the election had been rigged.

Mr Biden's new campaign is likely to focus heavily on the fight against the ideology on display during the 6 January riot. The video announcing his re-election bid opens with images of a mob of Trump supporters storming the Capitol.

"Every generation of Americans has faced a moment when they've had to defend democracy," he said. "This is ours. Let's finish the job."

As he campaigns, Mr Biden is likely to point to a number of accomplishments during his tenure, including job creation, efforts to prop up the economy in the wake of the pandemic and the passing of a bipartisan infrastructure law billed as a "once-in-a-generation" investment by the White House.

But he will face tough questions on his handling of immigration and the US-Mexico border, as well as on the chaotic US withdrawal from Afghanistan.

Mr Biden has also acknowledged that many Americans have raised "legitimate" questions about his age and ability to serve as President.

"And the only thing I can say is, watch me," he said earlier this year.