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Barack Obama closes the book on his presidency on Tuesday, with a farewell speech in Chicago that will try to lift supporters felled by Donald Trump's shock victory.

The First Lady Michelle Obama, Vice President Joe Biden and his wife Jill Biden will come along on for the ride. For Obama, it will be his final trip aboard Air Force One as president, though he'll use the plane to depart Washington for an unspecified destination next week just after Trump is inaugurated.

Obama's cross-country trek would be a sentimental trip down memory lane, were it not slap-bang in the middle of a tumultuous presidential handover.

Obama's final speech as president, before thousands who will gather at McCormick Place, is his last chance to try to define what his presidency meant for America. It's a fitting bookend to what he started eight years ago. It was in Chicago in 2008 that the nation's first black president declared victory, and where over the years he tried to cultivate his brand of optimism in American politics.

"I'll be thinking back to being a young community organiser, pretty much fresh out of school, and feeling as if my faith in America's ability to bring about change in our democracy has been vindicated," Obama said in a White House video previewing his speech.

I'll be thinking back to being a young community organiser, pretty much fresh out of school, and feeling as if my faith in America's ability to bring about change in our democracy has been vindicated

Obama said he's leaving his eight years in office with two basic lessons: that Americans are fundamentally good, and that change can happen.

"The system will respond to ordinary people coming together to try to move the country in a better direction," he said.

The system did respond, in November, to Americans who by and large rejected Obama's policies by electing Republican Donald Trump.

Obama and Democrats had warned against a Trump presidency in apocalyptic terms. So now Obama's daunting task – the closing act of his political career – is to explain how his vision of America remains relevant and achievable for Democrats in the Trump era.

No stranger to high-stakes speeches, Obama rose to national prominence on the power of his oratory. But this speech is different, White House officials said.

Determined not to simply recite a history of the last eight years, Obama directed his team to craft an address that would feel "bigger than politics" and speak to all Americans – including those who voted for Trump.

His chief speechwriter, Cody Keenan, started writing it last month while Obama was vacationing in Hawaii, handing him the first draft on the flight home. By late Monday Obama was immersed in a fourth draft, with Keenan expected to stay at the White House all night to help perfect Obama's final message.

In his weekly address Saturday, Obama acknowledged that the chaos of Washington makes it easy to lose sight of the role American citizens play in democracy. He said that while he leaves office with his work unfinished, he believes his administration made the US "a stronger place for the generations that follow ours."

Obama acknowledged that the chaos of Washington makes it easy to lose sight of the role American citizens play in democracy

Life after White House

Trump's unorthodox politics has thrown 55-year-old Obama's transition and post-presidency plans into flux.

Having vowed a smooth handover of power, Obama finds himself being increasingly critical of Trump as he prepares to leave office on January 20.

After that there will still be a holiday and an autobiography, but Obama could find himself being dragged backed into the political fray if Trump were to enact a Muslim registry or deport adults brought to the United States years ago by their parents.

Although he has said he will take a backseat in politics, Obama's second act could yet be as politically engaged as Jimmy Carter – whose post-presidency has remade his image as an elder statesman.

Many Obama aides who had planned to take exotic holidays or launch coffer-replenishing forays into the private sector are also reassessing their future and mulling a return to the political trenches.

Obama's foundation is already gearing up for a quasi-political role – funnelling idealistic youngsters into public life.

Obama's foundation is already gearing up for a quasi-political role – funnelling idealistic youngsters into public life

A nostalgic end

The trip to Chicago is not just for nostalgia, Keenan indicated.

"The thread that has run though his career from his days as community organiser to the Oval Office is the idea that if you get ordinary people together and get them educated, get them empowered, get them to act on something, that's when good things happen," he said.

"For him, as someone who started as a community organiser, whose campaign was powered by young people, ordinary people, we decided we wanted to go back to Chicago."

"Chicago is not just his hometown, it's where his career started."

And now it is also where Obama's presidential career will effectively end.

Agencies contributed to this report