In other words, state-level polls suggest that Biden has a national advantage of around 8 points.
Furthermore, all methods agree that Biden has a fairly considerable national advantage.
Examining state polls has the advantage of having many more data points to play with, so I feel pretty confident that they are giving us a decent snapshot. We are reviewing over 20 surveys and over 15,000 interviews. The aggregate margin of error is small.
Furthermore, we can examine the states that we expect to be at least somewhat competitive (i.e. those where the margin was last within 10 points) and those that we don’t think will be close in 2020.
In competitive states (where most of the state survey was conducted), there was an average swing of 6 points towards Biden compared to Clinton’s 2016 result. The same is true in non-competitive states.
At least from these state level data, it does not appear that neither candidate is increasing the score disproportionately in areas that were already friendly to him.
We can also test our data to see what would happen if the polls underestimated Trump as they did in 2016.
What I found out is that Biden would still be ahead, even with a 2016 mishap.
Focusing only on competitive states, polls have declared Trump by 2 points (RealClearPolitics) or 3 points (FiveThirtyEight). If polls in competitive states were out of what they were in 2016, Biden would still be ahead in states like Florida, Michigan and Pennsylvania.
The bottom line is Biden ahead right now nationally and in competitive states. The good news for Trump is that he has about six months to change the course of the campaign, which is more than enough to do it.