The political benefit or political effect of a suggestion, position, action, event, legislation, characteristic or movement is its tendency to give a relative advantage to one political party, or political side or person.
Virtually everything has a political benefit because almost nothing impacts all sides precisely the same. For example, a declining economy typically has a political benefit for the party not in control of the presidency. To take another example, gun control increases the dependency of all voters on government and thus has a predictable political benefit for leftist political parties.
Assessing the political benefit is essential to understanding the motivation for actions and statements, and anticipating them.