You are saying that %TO is people who came in and voted for Trump only and they did not vote for anything else on the ballot - just a single vote for Trump and left everything else blank. That's not correct. What Shiva is saying is that y=(%TO)-x where %TO (to use your variable) is the percentage of voters who voted for Trump but ALSO voted for other candidates - which makes them a mix of Reps, Dems, Indy, Green, etc. That's an important distinction because that %TO variable represents Dems, Reps, Indy, etc. voters who voted for Trump. And I think we can likely agree that they are probably heavily Independents because they didn't vote straight party Rep or Dem - but we don't know the mix. Here is Shiva explaining what the two types of voters are - tell me if you get a different sense from his explanation and whether you still think %TO represents people who only voted for Trump and left the rest of the ballot blank or whether you think they are people who voted for Trump but also voted for other party candidates down ballot. https://youtu.be/Ztu5Y5obWPk?t=920
UPDATE: here is good explanation between the straight party vote and individual vote in Michigan: https://www.lansingstatejournal.com/story/news/politics/2020/10/24/straight-ticket-option-michigan-ballots-2020-november/3726907001/
You are saying that %TO is people who came in and voted for Trump only and they did not vote for anything else on the ballot - just a single vote for Trump and left everything else blank. That's not correct. What Shiva is saying is that y=(%TO)-x where %TO (to use your variable) is the percentage of voters who voted for Trump but ALSO voted for other candidates - which makes them a mix of Reps, Dems, Indy, Green, etc. That's an important distinction because that %TO variable represents Dems, Reps, Indy, etc. voters who voted for Trump. And I think we can likely agree that they are probably heavily Independents because they didn't vote straight party Rep or Dem - but we don't know the mix. Here is Shiva explaining what the two types of voters are - tell me if you get a different sense from his explanation and whether you still think %TO represents people who only voted for Trump and left the rest of the ballot blank or whether you think they are people who voted for Trump but also voted for other party candidates down ballot. https://youtu.be/Ztu5Y5obWPk?t=920