Sen. Barack Obama of Illinois was elected the nation's 44th president yesterday, riding a reformist message of change and an inspirational exhortation of hope to become the first African American to ascend to the White House.

Obama, 47, the son of a Kenyan father and a white mother from Kansas, led a tide of Democratic victories across the nation in defeating Republican Sen. John McCain of Arizona, a 26-year veteran of Washington who could not overcome his connections to President Bush's increasingly unpopular administration.

Standing before a crowd of more than 125,000 people who had waited for hours at Chicago's Grant Park, Obama acknowledged the accomplishment and the dreams of his supporters.

"If there is anyone out there who still doubts that America is a place where all things are possible, who still wonders if the dream of our founders is alive in our time, who still questions the power of our democracy, tonight is your answer," he said just before midnight Eastern time.

"The road ahead will be long. Our climb will be steep. We may not get there in one year or even one term, but America, I have never been more hopeful than I am tonight that we will get there. I promise you: We as a people will get there."

The historic Election Day brought millions of new and sometimes tearful voters, long lines at polling places nationwide, and celebrations on street corners and in front of the White House. It ushered in a new era of Democratic dominance in Congress, even though the party's quest for the 60 votes needed for a veto-proof majority in the Senate remained in doubt early today. In the House, Democrats made major gains, adding to their already sizable advantage and returning them to a position of power that predates the 1994 Republican revolution.