You shouldn't have the threshold steadily creep downward as that just incentivizes drawing the process out by purposefully running terrible candidates until eve

You shouldn't have the threshold steadily creep downward as that just incentivizes drawing the process out by purposefully running terrible candidates until eventually the threshold is low enough not to matter. Instead you should have the threshold vary randomly with the actual amount only announced very shortly before the election when there isn't time for anyone to change strategies in response. Eventually the threshold will be low enough that there will definitely be a winner, but you don't know when it's going to happen so you need to treat every race as potentially the real one.