(CNN) -- Barack Obama has done what many just a year ago thought was impossible. He took on the most powerful family in Democratic politics and won.
Sen. Barack Obama on Tuesday became the first African-American to head the ticket of a major political party.
On Tuesday, Obama became the presumptive Democratic presidential nominee, marking the first time an African-American will head the ticket of a major political party.
The first-term senator captured the Democratic nomination by beating out Sen. Hillary Clinton, who was hoping to become the first female nominee.
He also had to campaign against the senator's husband, former President Bill Clinton, one of the great political talents of the 20th century who, at least going into the primary season, enjoyed widespread popularity among Democrats.
During one debate, Obama wondered out loud if he was running against the wife or the husband, given the former president's high profile on the campaign trail.
The two Democratic candidates fought a protracted and, at times, bitter battle that carried them through every state and brought nearly 35 million of their supporters to the polls.
When Obama declared his candidacy in February 2007, he faced an uphill battle. Clinton, a former first lady and New York senator, was the favored candidate.
Eleven months later, Obama proved the cynics wrong. He won Iowa's first-in-the-nation caucuses and, in what he called a "defining moment in history," he told his supporters "change is coming." Watch a recap of the primary season »
In the weeks that followed, what was once a wide field of candidates narrowed. Obama, once a long shot for the nomination, was in the final two.
His competition was fierce. Clinton, who boasted 35 years of experience and top-dollar supporters on her side, campaigned relentlessly.
She and Obama took the stage for more than 20 debates.
As the competition stiffened, their exchanges got heated. The two endured preacher-gate, Bosnia-gate, a bitter battle over the race card and other controversies that framed the race.
Questions arose over Obama's experience. Did a 46-year-old junior senator from Illinois have what it took to become the Democratic nominee?
Obama, the son of a white woman from Kansas and a father from a small village in Kenya, said yes.
Obama was used to defying expectations. He was the first African-American president of the Harvard Law Review. He was the third African-American since Reconstruction to be elected to the U.S. Senate.
But he tried to avoid being cast as the black candidate.
In a speech in March given to address the controversy surrounding his former pastor, Obama challenged Americans to take a closer look at race relations.
"I have brothers, sisters, nieces, nephews, uncles and cousins, of every race and every hue, scattered across three continents, and for as long as I live, I will never forget that in no other country on Earth is my story even possible," he said.
"It's a story that hasn't made me the most conventional candidate. But it is a story that has seared into my genetic makeup the idea that this nation is more than the sum of its parts -- that out of many, we are truly one."
Stop after stop, he preached a message of hope and unity.
His opponents criticized him for offering rhetoric and not solutions. But month after month, millions of voters believed.
On the night of his first victory, he told his supporters, "This was the moment when the improbable beat what Washington always said was inevitable."
Standing before a crowd of thousands Tuesday in St. Paul, Minnesota, Obama declared himself the Democratic nominee.
"Tonight we mark the end of one historic journey with the beginning of another -- a journey that will bring a new and better day to America," he said.
"Tonight, I can stand before you and say that I will be the Democratic nominee for president of the United States." Watch Obama declare himself the nominee »
Obama's rally was at the same arena that will house the 2008 Republican National Convention in September.
Previewing the battle ahead, Obama laid out his case against Sen. John McCain, the presumptive Republican nominee.
"This is our time. Our time to turn the page on the policies of the past," he said. Watch Obama take aim at McCain »
"It's not change when John McCain decided to stand with George Bush 95 percent of the time, as he did in the Senate last year."
But just hours earlier, McCain argued he represents the change the country needs. Watch McCain go on the offensive against Obama »
"No matter who wins this election, the direction of this country is going to change dramatically. But the choice is between the right change and the wrong change, between going forward and going backward," he said.
In recent weeks, McCain and Obama have provided a glimpse of the issues that will become themes of their general election fights.
McCain says Obama doesn't have the necessary experience. Obama counters, saying McCain will only bring four more years of President Bush's "failed policies."
The presidential hopefuls have already exchanged jabs over foreign policy, economics, housing woes and judgment.
The differences between the two are not subtle, and if recent scuffles are any indication of what lies ahead, the fight for the White House will be anything but subdued.