He squeaked into office by the narrowest of margins -- a Texas governor from outside the Washington orbit who promised a new brand of politics to heal a divided nation.
Yet George W. Bush never governed like a president who harbored uncertainties or self-doubt about his capacity to lead. He never lost the brash style that won him early successes and united the nation after the worst terrorist attacks in U.S. history.
He would fall back on his resolve in his administration's final days, as he turned his attention to his legacy.
But President Bush leaves office a diminished figure, shunned by his own weakened party while the nation faces unprecedented challenges at home and abroad.
In an ironic twist, the partisan vitriol he endeavored to end finally shows signs of abating -- under the leadership of a successor who ran as an antidote to the Bush years.
Bush forged ahead with an ambitious agenda in Washington -- deep tax cuts, vast changes in federal social programs, expansions of executive power and a broad remaking of energy and education policies.
Claiming a mandate by simply declaring its existence, his early successes mystified his critics. With guru Karl Rove directing the action, Bush won a stunning series of political victories.
He muscled a sometimes contradictory agenda -- big tax cuts, as well as the largest Medicare expansion since the program's inception -- through a Congress that was more than willing to follow his lead.
Sept. 11, 2001, reordered the nation's priorities, and President Bush was there to reap the political bounty: He gained seats for his party in the 2002 midterm elections, with national security issues prominent in the run-up to the Iraq war.
Even when that war proved unpopular and costly, he achieved his biggest political triumph -- a convincing reelection win, and more seats in Congress for his party, in 2004.
The "permanent" Republican majority he and Rove envisioned seemed attainable as Bush plunged himself into his most ambitious legislative effort yet: a partial privatization of Social Security.
But the president who boasted about "political capital" in the heady days after his reelection saw it spent within a matter of months, sapped by a lingering war in Iraq and Democrats who found an effective voice in united opposition.
Hurricane Katrina, with its image of utter incompetence, washed away what was left of the president's political standing.
The president's second term was defined by legislative paralysis, marked by record-low approval ratings, presidential candidates who ran from his shadow, anger and anxiousness abroad and, finally, the worst domestic financial crisis in generations.
In one piece of his legacy that the president himself has said he regrets, he never made Washington a less-hostile place.
"He's left our political institutions much more troubled than they were before," said Thomas E. Mann, a senior fellow at the Brookings Institution, a Washington-based think tank. "He didn't create the ideological polarization, but he magnified it."
In his final days in office, the president would fall back on post-9/11 security and his well-known resolve in making the case that his was a successful presidency.
"I hope [Americans] feel that this is a guy that came, didn't sell his soul for politics, had to make some tough decisions, and did so in a principled way," Bush told ABC's Charles Gibson in an interview in December.
"I don't spend a lot of time really worrying about short-term history. I guess I don't worry about long-term history, either, since I'm not going to be around to read it," he added. "But look, in this job you just do what you can. The thing that's important for me is to get home and look in that mirror and say, 'I did not compromise my principles.' And I didn't. I made tough calls."
The public wasn't with him in the end. The most recent ABC News/Washington Post poll showed a 68 percent disapproval rating, dragged down by economic duress and a still-unpopular war.
It wasn't always this way for this president.
A polarized country rallied behind him after the 9/11 terrorist attacks, and his approval ratings reached a high of 92 percent.
"He had this huge burst of unity, used it well and nurtured it through Afghanistan," said Bruce Buchanan, a government professor at the University of Texas who has followed Bush's career since his days as governor of Texas.
That unity began to crumble -- like so much surrounding his presidency -- over the Iraq war.
President Bush's push to oust Saddam Hussein from power soon became more than a foreign-policy initiative; the president and his allies used it as a wedge issue against Democrats in the run-up to the 2002 elections.
"After 9/11, he had a country that said, 'We're ready to follow,' " Rahm Emanuel, President-elect Barack Obama's incoming chief of staff, told ABC News before he was tapped for the new post. "There was so much we could have done. But he said, 'Go shopping,' and then he divided the nation."
The hyper-political push for war cost him the support of Democrats. There would be no more big bipartisan successes for him to celebrate, such as his signature education law, No Child Left Behind.
Republicans stayed with him, however, and while they controlled Congress. That was often enough. It kept him politically potent through the 2002 and 2004 campaigns.
But new spending programs and other breaks with conservative dogma hurt the president's standing inside the GOP, and he never really worked the Washington game to develop relationships with members of Congress.
In his second term, Democrats scuttled Social Security reform even before the president could file a bill. Opposition to Bush became their organizing principle -- the formula they rode to success in 2006 after the botched federal response to Hurricane Katrina and a continuing war left Bush politically crippled.
Then came 2007, and with it a new chance to work with Democrats on an issue that had long been close to his heart -- immigration.
But in that case, Bush's fellow Republicans abandoned him, unwilling to follow a politically damaged president down a road they did not favor.
It was as if the Bush-Rove vision came full circle: They fostered a polarized political environment, and then saw their grand policy goals shattered by that very climate, where bipartisan cooperation was impossible.
"They created a political situation where nothing could get done," Buchanan said. "President Bush has demonstrated the fine line between leadership and stubbornness."
Bush's legacy will perhaps always be tied to the Iraq War, and on that measure it's too early to make judgment.
Bush himself has often said that he'll leave his legacy to the judgment of historians. But as he retires to Texas, it is a complex mix of success and failure that define the two terms of George W. Bush.
"He achieved more in the way of policy changes with less in terms of mandate and public support than any president in memory. If you're grading him in terms of batting average, you'd grade him rather high," Mann said.