Logical fallacies are common errors in reasoning that weaken arguments. Examples include:
Ad hominem: Attacks character instead of arguments (e.g. Trump: "look at that face: would anyone vote for that?").
False analogy: Compares dissimilar items, weakening the argument.
Straw man: Oversimplifies an opponent's view and attacks that version.
Circular argument: Restates the argument without proving it.
Slippery slope: Concludes that one action will lead to a series of negative outcomes.