You need to consider both statistical and systematic errors.
10,000 responses is enough to give you a statistical error of 1%, but the systematic error on 2016 was around 2%, and you can’t beat that down with more responses.
Also, the red team has a structural advantage of a few percent.
All of this means that the blue team needs to be up by at least 5% in national polls before they can be considered to be ahead.
You need to consider both statistical and systematic errors.
10,000 responses is enough to give you a statistical error of 1%, but the systematic error on 2016 was around 2%, and you can’t beat that down with more responses.
Also, the red team has a structural advantage of a few percent.
All of this means that the blue team needs to be up by at least 5% in national polls before they can be considered to be ahead.