Barack Obama said Sunday that the front-runner for his party's nomination, Hillary Rodham Clinton, does not offer the break from politics as usual that voters need.
Both Clinton and her husband, former President Bill Clinton, have criticized Obama for his lack of political experience.
Obama said he understands their argument.
"They want to make the argument that Senator Clinton is just an extension of the Bill Clinton presidency," Obama said in an interview with The Associated Press. "They've been the dominant political family in the Democratic Party for the last 20 years now. So it's not surprising that they want to focus on their longevity."
But, Obama said: "My belief is that the American people are looking for a fundamental break from the way we've been doing business."
Obama said his opposition to the Iraq war before combat began shows his experience. Clinton voted to authorize military action in Iraq.
"On the single most important foreign policy issue of our time, I got it right," Obama said.
This week marks the fifth anniversary of a speech Obama gave in 2002 opposing the Iraq war, and he will spend the week revisiting that address and discussing the foreign policy challenges he says it has created.
Obama attended religious services at Baptist churches Sunday, showing little concern about the third-quarter fundraising deadline that ends Sunday night. He raised more than $58 million (41 million EUR) in the first six months of the year.
"We've done a remarkable job fundraising," Obama said, adding his campaign has more than 300,000 donors. "We have more donors giving $200 (141 EUR) or less than all the other Democratic candidates combined."