Also called Ignoratio Elenchi, Irrelevant Thesis, Smoke Screen, Wild Goose Chase or Wild Tangent.
Attempting to support one proposition or hide its weakness by arguing for a different one entirely, or dodging the main argument by going off on a tangent. This fallacy is committed when someone introduces irrelevant material to the issue being discussed, so that everyone's attention is diverted away from the points made, towards a different conclusion, in order to "win" the argument.
This sort of "reasoning" has the following form:
This sort of "reasoning" is fallacious because merely changing the topic of discussion hardly counts as an argument against a claim.
"You may claim that the death penalty is an ineffective deterrent against crime — but what about the victims of crime? How do you think surviving family members feel when they see the man who murdered their son kept in prison at their expense? Is it right that they should pay for their son's murderer to be fed and housed?"
"We admit that this measure is popular. But we also urge you to note that there are so many bond issues on this ballot that the whole thing is getting ridiculous."
"You know, I've begun to think that there is some merit in the Republican's tax cut plan. I suggest that you come up with something like it, because If we Democrats are going to survive as a party, we have got to show that we are as tough-minded as the Republicans, since that is what the public wants."
"I think there is great merit in making the requirements stricter for the graduate students. I recommend that you support it, too. After all, we are in a budget crisis and we do not want our salaries affected."
Works only if your opponent is very absent-minded.
If your opponent attempts to make a red herring, bring him back to the point at issue.