Also be good if one of them could be a Southerner.

Well, in fact Kerry is on the record saying that if he gets the nomination he'll choose a Southerner as his running mate...Edwards maybe?

 Whoever wins the nomination, all the candidates owe their wholehearted support to the nominee.

One of the best moments from the last debate I watched came when, following several attacks by his fellow candidates when they were told they could each direct a question to one of the other candidates (most went after Dean), Dean asked the group on stage with him if they would all pledge support to whoever won the nomination...Dean then raised his hand saying he would and looked across the stage at his obviously surprised comrades...there was a breif moment of bewilderment...the director of the broadcast quickly went to a wide shot of the stage...the candidates looked around at eachother for a second and then began raising their hands...