DENVER — Senator Edward M. Kennedy, struggling with brain cancer, arrived on Monday night at the Democratic National Convention in a triumphant appearance that evoked 50 years of party history as Democrats gathered to nominate Senator Barack Obama for president.

Mr. Kennedy’s appearance wiped away, at least for the evening, some of the tension that continued to plague the party in the wake of the primary fight between Mr. Obama and Senator Hillary Rodham Clinton. It also represented an effort by the Obama campaign to claim the Kennedy mantle, and it set the stage for the second part of what was designed to be an emotionally powerful two-act evening: an appearance later by Michelle Obama, who began a weeklong effort to present her husband — and his entire family — as embodiments of the American dream.

“You see, Barack doesn’t care where you’re from, or what your background is, or what party, if any, you belong to,” said Mrs. Obama, without explicitly mentioning the racial undercurrents that have swirled around her husband’s candidacy. “You see, that’s just not how he sees the world. He knows that thread that connects us — our belief in America’s promise, our commitment to our children’s future — he knows that that thread is strong enough to hold us together as one nation even when we disagree.”

At the end of the evening’s proceedings, Mr. Obama appeared before the convention by video hookup, with his young daughters, Malia and Sasha, joining his wife on stage for what was clearly intended to transmit a loving American family tableau.