USC/Dornsife tracking poll megathread

[TiltsAreUnderrated]

Each data point tracks seven days and about 1000-3000 voters. 538 treats both of the first projections as LVs and ignores the last two types, but there are four: traditional responses, probability-based projections (which incorporates respondents' answers regarding their own beliefs about the probability of them voting for X or Y, etc.), expectations about how others in the state will vote and "social circle voting" (expectations about how one's social circle will vote).

The probability-based one just gives Biden, Trump and someone else, and the traditional question prompts for Biden, Trump, Jorgensen, Hawkins, undecided and would not vote (and then removes "would not vote" responses for the final % projections). These responses are still weighted.

[TiltsAreUnderrated]

Reading the methodology statement a bit more carefully, the probabilistic personal vote topline (the one that generates Biden +13% instead of the traditional sample's Biden +14%) seems to incorporate the following: "Of all the people who live in your state and are likely to vote, what percentage do you think will vote for Biden, Trump, Someone else?"

This same question is posted later in the document as part of the Winner Expectations question and I assume its inclusion in the probabilistic voting sample is a mistake given that 538 still lists this as a valid poll.

[TiltsAreUnderrated]

https://twitter.com/Politics_Polls/status/1300764918199783425?s=19

+10% using the traditional as opposed to the probabilistic sample, but the trend has been steady in both results.

[TiltsAreUnderrated]

Probablistic:
Biden 51% (-1)
Trump 42% (n/c)

Traditional:
Biden 52% (n/c)
Trump 41% (n/c)

[TiltsAreUnderrated]

Probabilistic

Biden 51% (n/c)
Trump 43% (+1)

Traditional

Biden 51% (-1)
Trump 42% (+1)

[TiltsAreUnderrated]

https://twitter.com/Politics_Polls/status/1304294698589335552

Probablistic
Biden 52.7 (-0.3)
Trump 41.1 (+0.3)

Traditional
Biden 54.8 (-0.4)
Trump 39.8 (+0.1)

[TiltsAreUnderrated]

Probablistic
Biden 52.7 (-0.1)
Trump 41.1 (+0.5)

Traditional
Biden 54.3 (n/c)
Trump 40.5 (+0.5)

[TiltsAreUnderrated]

Probabilistic
Biden 52.8 (+0.1)
Trump 40.6 (-0.5)

Traditional
Biden 54.3 (-0.5)
Trump 40.0 (+0.2)

Can someone explain in layman's terms the difference between the two methodologies?

If I'm interpreting the methodology document correctly, the key differences are as follows:
 - Probablistic questioning differs in that it starts by requesting respondents to estimate (in percentage terms) the chance that they will vote and, given that they will vote, the chance that they will vote for Trump, Biden or "someone else" (the three options given). It incorporates these into its likely voter weightings (which depend on other factors shared by the traditional voting weightings)

 - Traditional questioning prompts for Biden, Trump, Hawkins, Jorgensen, undecided or "would not vote" (instead of asking voters to give the chance that they'll vote for a candidate, they simply incorporate voters who lean towards a given candidate or list themselves as completely undecided). It then removes people who responded "would not vote" to generate the sample's final results.

My guess is that prompting for "someone else" leads to more inflation of the third party vote than prompting for Hawkins and Jorgensen, even though doing the latter is likely to suggest higher polling numbers for them than those which will actually manifest on election day. Traditional voting also probably doesn't take into account just how strongly "leaners" lean towards a given candidate (beyond the crude "definitely voting for X/leaning towards X" divide).

[TiltsAreUnderrated]

Probablistic
Biden 51.7 (-1)
Trump 42 (+0.9)

Traditional
Biden 52.8 (-1.5)
Trump 41.8 (+1.3)

[TiltsAreUnderrated]

Probablistic:
Biden 50.3% (+0.1)
Trump 42.7% (-0.8 )

Traditional:
Biden 49.8% (-0.2%)
Trump 43.3% (-0.4%)

[TiltsAreUnderrated]

Probablistic
Biden 50.1% (-0.1)
Trump 42.7% (n/c)

Traditional
Biden 50.7% (+0.9)
Trump 43.2% (-0.1)

[TiltsAreUnderrated]

Probablistic:
Biden 51.1% (+0.4)
Trump 41.8% (-0.3)

Traditional:
Biden 52.3% (+0.7)
Trump 41.7% (-0.5)

[TiltsAreUnderrated]

Using the two-week sample in this post.

Probablistic:
Biden 51.4% (n/c)
Trump 41.9% (n/c)

Traditional:
Biden 52.4% (-0.1)
Trump 41.7% (-0.1)

[TiltsAreUnderrated]

Probablistic:
Biden 51.3% (-0.1)
Trump 42.1% (+0.2)

Traditional:
Biden 52.1% (-0.3)
Trump 42% (+0.3)

[TiltsAreUnderrated]

Probabilistic:
Biden 51.2% (-0.1)
Trump 42.2% (+0.1)

Traditional:
Biden 51.9% (-0.2)
Trump 42% (n/c)

[TiltsAreUnderrated]

Probablistic:

Biden 51.3% (-0.1)
Trump 42.6% (+0.1)

Traditional:

Biden 52.1% (n/c)
Trump 42.2% (-0.1)

[TiltsAreUnderrated]

Probabilistic:
Biden 51.1% (-0.2)
Trump 42.7% (+0.1)

Traditional:
Biden 51.8% (-0.3)
Trump  42.3% (+0.1)

[TiltsAreUnderrated]

Probablistic:
Biden 51.1% (n/c)
Trump 42.9% (+0.2)

Traditional:
Biden 51.9% (+0.1)
Trump 42.4% (+0.1)

[TiltsAreUnderrated]

Probablistic:
Biden 51.1% (n/c)
Trump 42.9% (n/c)

Traditional:
Biden 51.8% (-0.1)
Trump 42.6% (+0.2)

[TiltsAreUnderrated]

Probabilistic:
Biden 51.3% (+0.2)
Trump 43.3% (+0.4)

Traditional:
Biden 52.1% (+0.3)
Trump 43.0% (+0.4)

[TiltsAreUnderrated]

Probablistic:
Biden 52.2% (-0.3)
Trump 42.7% (+0.3)

Traditional:
Biden 53.1% (-0.1)
Trump 42.2% (+0.2)

[TiltsAreUnderrated]

Probablistic:

Biden 52.6% (-0.2)
Trump 42.4% (+0.1)

Traditional:

Biden 53.0% (-0.5)
Trump 42.0% (+0.3)

[TiltsAreUnderrated]

10/10

Probabilistic:
Biden 53.4% (+0.3)
Trump 41.6% (-0.3)

Traditional:
Biden 54.0% (+0.4)
Trump 41.1% (-0.3)