When Barack Obama began his candidacy for the White House 20 months ago, most Americans knew next to nothing about the young senator from Illinois, barely two years into his first term in federal office.

After his performance in 2004, some Democratic activists had marked him as the best convention speaker since Ted Kennedy, Ann Richards or Mario Cuomo. Others had read his book "Dreams From My Father" and had declared him their finest literary talent since Ted Sorensen was ghostwriting for John F. Kennedy. Still others remarked on the fact that Obama had been prescient in his opposition to the U.S. attack on Iraq.

But no one knew much about his political skills or his ideology, so he was generally underestimated as a threat to Hillary Clinton and the others who lined up for the 2008 prize.

What we have learned since then has been impressive. The most basic question about him – or anyone seeking the presidency – is whether he has the capacity to lead the country and manage the government. Nothing in Obama's history – lawyer, organizer, state legislator and back-bench senator – had demonstrated extraordinary skills. The proof had to come from the campaign itself.

As soon as I saw him on the small-town circuit in Iowa, two things became clear. He could generate votes by the force of his rhetoric and personality; he was not yet a celebrity, but he already had the capacity to convert strangers into friends. And second, he had a cadre of people working for him who knew what they were doing. Though many were in their first presidential campaign, they were not amateurs. They understood their responsibilities and went about their work with minimal waste of energy. Somehow, this young senator had developed a battle plan for an awesomely intimidating process. Mitt Romney, with his Harvard MBA, was no more efficient than Obama.

Of course, running a good campaign is not a guarantee of success as president. Jimmy Carter figured out how to move from Plains, Ga., to the White House, a journey almost as implausible as Obama's, but he didn't know how to govern.

Obama has been Carteresque in the extravagance – and vagueness – of his promises to change Washington. But he is not afflicted with Carter's intellectual-moral contempt for other politicians, the trait that wrecked Carter's relationship with a Democratic Congress. On the contrary, Obama moves well among the political insiders, even while presenting an outsider's visage to the public.

What we have learned of Obama's programs puts him squarely in the liberal tradition of the party. Unlike Bill Clinton, he has not tried to spell out the ways in which he would propose to rewrite Democratic policy. As a result, we can only guess what his real priorities would be. One can imagine serious debates within an Obama administration and between his White House and Congress.

In what history may record as his singular achievement – dealing with the American dilemma of race – he had the largely unappreciated help of his opponent, John McCain, who ruled out covert racial appeals used by politicians of both parties in the past.

But Obama himself demonstrated repeatedly how to bridge the racial divides that still remain, by emphasizing his calm good judgment and respect for others. As a symbol of that national maturity, he carries a powerful positive message to the world.

Obama is not, any more than other politicians, a paragon. He reneged on his promise to use public funds for his general election campaign, driving a stake in the heart of the post-Watergate effort to reform the campaign finance system. He rejected McCain's invitation to joint town hall meetings – opening the door to the kind of tawdry exchange of charges that we have seen. In both instances, he put his personal goals ahead of the public good – a worrisome precedent.

But he has engendered widespread enthusiasm in a jaded and cynical public, especially among young people. And if he does not disillusion them in the years ahead, that would be a real gift to the nation.

Reach David Broder at davidbroder@washpost.com.