It is unprecedented in modern times for the candidate and his Veep to campaign together beyond a few appearances immediately following the convention. Campaigns send the Veep out seperately to double there campaign coverage.
But McCain hasn't been able to draw a crowd for months, and that all changed when he picked Palin as his running mate. Now he's forced to continued to campaign with her, because of the embarrassment he will suffer when she continues to draw large crowds (by far the largest of his campaign) and he goes back to playing the nursing homes.
It's all very odd.