The coordination of the ad tells us that the motivations of the group presenting it is to reach the typical American parent/spouse who is spending their time and gas money picking up groceries and doing other things to take care of their family, but instead of being rewarded for their hard work and dedication, if they vote for Kerry, they will instead be severely penalized through higher taxes. Ultimately, the motivation is to win the election. However, the more indirect motivation is to discredit John Kerry and the "liberals" (a term that is spoken as if it were the most reprehensible term on earth) by making it seem as if they are 'out to get' the average American. The implication is that Kerry does not have the best interests of the American public at heart.

Interestingly, there is never anything said positive about Bush in this ad. All of the announcer's comments and the woman's thoughts are based on negative reflections of Kerry. There is a never a moment when the announcer implies that Bush would not raise taxes or that Bush is looking out for the average American. These thoughts are merely expected to be inferred by the listener because they are in contrast with what the announcer is saying about Kerry. Since everyone knows that Republicans and Democrats are in contrast, then it is supposed to be naturally...

This way, Bush is not accountable for breaking a promise not to raise taxes because he never actually said he would not raise taxes -- he merely said that Kerry definitely would. Therefore he is absolved of responsibility because he cannot be held accountable for what the public "assumes" or interprets from his advertisements.
This is very manipulative way to influence the voting public, but it is certainly not an unusual tactic for political advertisements. Not only are the statements made against Kerry exaggerated and taken completely out of context, but they are left hanging in the air with no promise from Bush that he would do anything different. The coordination the view/listener makes between Bush and lower taxes based on the attacks on Kerry is merely a case of the viewer/listener filling in the blanks. That way Bush is not held to any "read my lips"-type of backpedaling that his father experienced. For all the listener knows, Bush plans to raise gas taxes 20 times; but the fact that he is lambasting Kerry for supposedly wanting to raise them 10 times seems to automatically imply that Bush would not do that. Ultimately, that is what is at the heart of the rhetorical content of this advertisement.