Maverick: From its archaic definition of "an unbranded range animal ; especially : a motherless calf," to its more contemporary definition of "an independent individual who does not go along with a group or party," there is no truly endearing presidential quality in the word maverick.
When we think presidential, we (middle to bottom America) want to think strong, resolute, caring, tolerant, ready and able to work with others at finding solutions to problems...get my drift? We don't want to envision some own-way, stand-alone, eccentric one-man show, which is all suggested in the word maverick. And if maverick was used to try to distance McCain from Bush, it failed. Descriptions like smart, tolerant, ready and willing to work with others at finding solutions to domestic and global problems, and such like would work wonderfully at distancing McCain from Bush, not maverick.