Fallacy Ad Hominem

Being a close follower of the presidential race, I have run into the ad hominem fallacy quite often. When a candidate has no response to the other candidates questions, positions, etc. they often settle for attacking that candidates character in some way. For example, the current economic crisis has seen a sharp jump in polling favoring Sen. Barack Obama. Rather than responding to the crisis with a plan of their own, Sen. McCain's campaign has gone on the offensive trying to bring up Sen. Obama's distant relationships with negative figures. Another example would be person A saying, "We shouldn't go into Iraq as there is not enough evidence to wage a war," while person B would respond by saying, "You're not patriotic."