Senator Barack Obama claimed the Democratic presidential nomination on Tuesday night, prevailing through an epic battle with Senator Hillary Rodham Clinton in a primary campaign that inspired millions of voters from every corner of America to demand change in Washington.

A last-minute rush of Democratic superdelegates, as well as split results from the final primaries in Montana and South Dakota, pushed Mr. Obama over the threshold of 2,118 delegates needed to be nominated at the party’s convention in Denver in August. The victory for Mr. Obama, the son of a black Kenyan father and white Kansan mother, broke racial barriers and represented a remarkable rise for a man who just four years ago served in the Illinois State Senate.

“You chose to listen not to your doubts or your fears, but to your greatest hopes and highest aspirations,” Mr. Obama told supporters at a rally in St. Paul. “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. Because of you, tonight, I can stand before you and say that I will be the Democratic nominee for president of the United States.”

Mrs. Clinton paid tribute to Mr. Obama, but she did not leave the race. “This has been a long campaign and I will be making no decisions tonight," Mrs. Clinton told supporters in New York. She said she would be speaking with party officials about her next move.