Unmeasurable? Those votes for X were each the one vote that made X win. If any single one of those votes had not been cast, it would have been a tie. Those votes all mattered as much as a vote can possibly matter.
When you win by 1000000 to 1, then all the winning votes mattered for an unmeasurable amount.
By measurable, I mean objectively. Mattering "as much as a vote can possibly matter" is not objective. Because in that case, all the ones who did not express their vote also had a decisive (non-)vote. Their (non-)vote made the same difference.
All of this does not make any sense. Voting is by essence a collective action, and can not be divided into individual actions.
Well it can, of course, but is has the same kind of meaning as wondering which of somebody's cells triggered his/her cancer, or what is the responsibility of a given car in a given traffic jam (especially those created by slowing cars on the opposite lane of the one having a real accident).
When you win by 1000000 to 1, then all the winning votes mattered for an unmeasurable amount.