Barack Obama turned his focus to a US general election showdown with John McCain and said the Republican White House candidate would continue the "failed policies" of President George W. Bush.
Mr Obama gathered momentum in his battle with Hillary Clinton for the Democratic presidential nomination with endorsements from seven more senior party figures and a labor union, as well as strong praise from former Democratic rival John Edwards.
"Let's assume Barack is the nominee, because it's certainly headed in that direction," Edwards told NBC's "Today" show. He said Mr Obama could unify the party and had a better chance than Mrs Clinton of winning November's election against Mr McCain.
Mr Obama, an Illinois senator, largely ignored Mrs Clinton during his first campaign stop since taking a commanding lead in the Democratic race on Tuesday by winning a primary election in North Carolina and narrowly losing Indiana.
But he took direct aim at Mr McCain, saying he had fundamental differences with the Arizona senator on issues like the Iraq war, taxes, gasoline prices and health care.
"John McCain wants to continue George Bush's war in Iraq, losing thousands of lives and spending tens of billions of dollars a month to fight a war that isn't making us safe," Mr Obama said in Beaverton, Oregon.
"Senator McCain is running for president to double down on George Bush's failed policies. I am running to change them and that is what will be the fundamental difference in this election when I am the Democratic nominee for president."
Mrs Clinton struck a conciliatory tone at a Kentucky Democratic Party dinner in Louisville.
She only mentioned Mr Obama, who would be the first black president, to draw comparisons between women and blacks - two groups she said had suffered greatly under the original US constitution.
"Neither Sen. Obama nor I nor many of you were fully included in the vision of our founders," she said.
"Once we have a nominee, I know in my heart we will come together as a party," she said, heaping criticism on McCain. "What he's offering is not what America needs."
Before Mrs Clinton took the stage, some audience members taunted her with chants of "Obama! Obama!"
Mr Obama picked up seven more "superdelegates" -- the group of nearly 800 party leaders and elected officials not bound by the state-by-state contests who are free to back any candidate at the Democratic nominating convention in August.
He was also endorsed by the American Federation of Government Employees, representing 600,000 federal workers.