It is common for arguments to conclude that one thing causes another. But the relation between cause and effect is a complex one. It is easy to make a mistake. In general, we say that a cause C is the cause of an effect E if and only if: (1) Generally, if C occurs, then E will occur, and (2) Generally, if C does not occur, then E will not occur either. We say "generally" because there are always exceptions. For example, we say that striking the match causes the match to light, because: (i) Generally, when the match is struck, it lights (except when the match is dunked in water), and, (ii) generally, when the match is not struck, it does not light (except when it is lit with a blowtorch). Many writers also require that a causal statement be supported with a natural law. For example, the statement that "striking the match causes it to light" is supported by the principle that "friction produces heat, and heat produces fire".
The object or event identified as the cause of an effect is a genuine cause, but insignificant when compared to the other causes of that event. Note that this fallacy does not apply when all other contributing causes are equally insignificant. Thus, it is not a fallacy to say that you helped cause defeat the Tory government because you voted Reform, for your vote had as much weight as any other vote, and hence is equally a part of the cause.