>What if 80% of the public follows the political issues and is well informed? What if 40% have rational reasons to vote for the right-wing, and 40% have rationa

>What if 80% of the public follows the political issues and is well informed? What if 40% have rational reasons to vote for the right-wing, and 40% have rational reasons to vote for the left-wing? Then it is the most ignorant, badly informed 20%, voting somewhat randomly, that will determine every election. I feel like I see this sort of analysis a lot. You pick whatever set of voters you want to focus on, hold all other voters fixed, and declare your set as "deciding" the election. As if their votes count while others don't. By what possible metric does this supposed 20% "decide" the election, but any other 20% bloc does not?