Clinton, too, personally apologised to Obama when they met on the tarmac of the Reagan National Airport in Washington DC, just ahead of the final Democratic debate in Iowa before the January 3 caucus.
In the debate, organised by the Des Moines Register, both Obama and Clinton focused on change.
According to Chris Cillizza of the Washington Post, Obama used almost every answer to make his case that real change in politics is only possible if he is the nominee.
And here's what Clinton -- daughter Chelsea was there to support her -- had to say: 'Everybody on this stage has an idea about how to get change. Some believe you get change by demanding it, some believe you get it by hoping for it. I believe you get it by working hard for change.'
Did you know? In September 2007, President George Bush predicted Hillary Clinton would be the Democrat nominee for president.
Image: Chelsea Clinton, daughter of former President Bill Clinton and Democratic presidential hopeful US Senator Hillary Clinton chats with former Iowa Governor Tom Vilsack as they wait for the start of The Des Moines Register presidential debate.
Photographs: Scott Olson/Getty Images
Also read: The real tragedy of the Presidential elections
External link: The Register debates