This article in PC World Magazine, based on a survey, purports that the strongest VP candidate for either party is Colin Powell.
Powell's links to the current Iraq war didn't seem to bother survey respondents, said Kevin Karty, vice president of analytics at Affinnova. Powell, in early 2003, argued for the war before the United Nations Security Council, but since he has left the Bush administration, he's criticized its handling of the war.
"There might be an indication that people are willing to give him a pass [on Iraq]," Karty said. "He seems to be an extremely credible figure ... and he's trustworthy."
UPDATE: C'mon, people, stop taking it so seriously.