Debate over debates

Get ready to hear the numbers 21 and 4 over and over again during the next few days.

Twenty-one is the total of Democratic presidential debates over the past year -- and Barack Obama says that is plenty.

He says he's not ducking another debate and has not closed the door to one after the Indiana and North Carolina primaries on May 6. But he and his campaign say they want to spend the next nine days talking directly to the voters of the two states.

Four is the number of head-to-head debates between Obama and Hillary Clinton since the rest of the field fell away for the nomination -- and Clinton says that is not enough.

She is challenging Obama to face off before May 6 anytime, anywhere and one-on-one without any moderators. She says voters in Indiana and North Carolina deserve their own debates.

The last debate, April 16 in Philadelphia, was also the most watched, drawing nearly 11 million viewers to the first aired on a broadcast network during weeknight primetime. Critics, including Obama and his supporters, said the debate focused far too much on the controversies of the moment and far too little on substantive issues.