History will remember Barack Obama as America's first black president. But his eight years in office have throroughly shaken up America's role in the world and the political spectrum at home.

"How's that hopey-changey stuff working out for ya?" sneered Sarah Palin, the defeated 2008 Republican vice presidential nominee.

It was February 2010, scarcely a year after Obama swept into the White House. He had promised halcyon days of hope and change -- an end to partisan gridlock and bloody expeditionary wars -- but he was struggling to live up to his own hype.

Obama's first year in office saw four million Americans lose their jobs. Hundreds more lost their lives in "forever wars" in Iraq and Afghanistan. Republicans and Democrats seemed as dislocated as ever.

Senate Republican leader Mitch McConnell set the tone at the outset: "The single most important thing we want to achieve is for President Obama to be a one-term president."

Obama had tried to temper expectations. "We are living through difficult and uncertain times," he said during an inaugural congressional address that surprised with its gloominess.

But his own soaring rhetoric -- at times on par with Winston Churchill or John F. Kennedy -- had set the bar too high.

He wasn't helped by the Nobel Committee, which made him a peace laureate months after he took office.

"I would be remiss if I did not acknowledge the considerable controversy that your generous decision has generated," he said accepting the prize in Oslo.

Fast forward to the end of Obama's labors and the economy is in a slow but steady convalescence.

Massive fiscal stimulus and historically unparalleled monetary easing -- what former Treasury secretary Tim Geithner would describe as a "wall of money" -- ameliorated the crisis, but the recovery was uneven.

The threat of jihadist attacks continues and wars in Iraq and Afghanistan rage, but with a much lighter US footprint and toll in blood.

- Intervention -

If George W. Bush's unilateralism had made him an international pariah, Obama's pledge to cooperate and restore America's reputation helped make him a rock star.

His credo that "no one nation, no matter how large or how powerful, can defeat such challenges alone" was met with adulation by 200,000 fans in Berlin.

At times, Obama seemed to positively embrace the end of post-war US hegemony.

He defined the national interest much more narrowly and eschewed intervention, even when his own red lines were breached and America's reputation was damaged.

The cost in blood and treasure of being the world's policeman had been too great. The Great Recession had shown that commitment was probably unsustainable too.

Instead, he looked to allies to carry their weight in their neighborhoods. In Libya and elsewhere, the United States would "lead from behind."

But his timing could scarcely have been more problematic.

The retrenchment of US power came as rivals became more bellicose and allies in Europe -- beset by financial, social and security crises -- were at their weakest and most parochial.

In Xi Jinping and Vladimir Putin, China and Russia had more powerful leaders than at any time since Mao Zedong or Leonid Brezhnev.

In Turkey, the century-long pro-western legacy of Mustafa Kemal Ataturk was unraveling.

Meanwhile Obama's "pivot to Asia" came as Arab citizens were finding their voice and looking for support against brutal regimes.

Nowhere have the shortcomings of Obama's doctrine been more relentlessly probed than in Syria, where hundreds of thousands have died as Obama has refused to intervene, except to tackle jihadists who took advantage of the vacuum.

- Tribalism -

At home, Obama's presidency has seen similar seismic shifts.

Since the 1990s, US politics had been dominated by pitched battles between right and left, conservatives and liberals. His term may be remembered as a time when the page turned.

Through an international accord to tackle climate change, Obama displayed that public opinion at home and international consensus had moved beyond Republican denials about the existence of global warming.

A momentous week in June 2015 encapsulated the sense that Obama had put the "culture wars" to bed.

In a few short days he saw off a legal challenge to his signature healthcare law, the Supreme Court backed gay marriage and in a searing eulogy for Clementa Pinckney -- a black preacher killed by a white gunman -- Obama took aim at gun laws and nostalgia for the Deep South of yesteryear.

The Confederate flag, he insisted, was "a reminder of systemic oppression and racial subjugation."

The 2016 election to replace Obama is being fought on different terrain.

The left-right divide has blurred. No one has been more surprised or repulsed by Donald Trump's movement than conservatives or national security within the Republican Party.

In the wake of the Great Recession, the fault lines in post-Obama politics look economic: Globalist versus nativist, populist versus liberal.

But America's politics have also moved from partisan to tribal, with Democrats and Republicans flocking to support their own deeply flawed candidates.

Meanwhile even Obama's fiercest critics acknowledge his White House has been bereft of ethics and sex scandals.

"Professor Obama" -- once criticized as too cold and out of touch -- leaves office with soaring public approval ratings that are approaching levels enjoyed by former presidents Bill Clinton and Ronald Reagan.

His legacy is not yet fully formed, but as he leaves office some 55 percent of Americans believe the hopey-changey stuff worked out.