A C+ poll of 500 LV out of Utah just moved 538's presidential forecast 1.3% all by itself

[Persondem]

This is why I am losing respect for 538. 1 poll showing T up 5 in a very red state should have next to no effect on the forecast. Instead it dropped Clinton's chances 1.3%. How is that based on anything real? If anything, the fact that Clinton is only 5 points down in Utah should be a plus for her chances.

[getagrip_already]

1. not defending 538.... even nate said its failing, but....

How do you know the single new poll is what moved it?

538 drops old polls in their weighting factor. that is automatic, and percentages sometimes change even with no new polls. All that happened was a good poll got old and its weighting factor fell, so it counted less.

With tightening polls, those older polls are the better ones, so as they fall in weight the perceentages change downward.

It's too complicated. I've found that sometimes, the more data you try to stuff into a model, the worse it does.

[Ace Rothstein]

2. They show the changes with every one of their updates.

[vdogg]

3. A ton of crappy republican polls just came out

One showed CO tied with Trump winning 18-35. Another had him with 22% black support and 47% Hispanic. These polls are put out to fuck with the RCP averages and 538 to give the illusion of a Trump surge. Ignore them.

[bigdarryl]

4. I don't know why DU'ers put so much stock in 538

Daily Kos radio this morning Amundo ,Greg Dorkin and others were saying how ridiculous Nate Silver was by putting all.these partisan polling companies in his data that changes his percentages daily

[budkin]

5. This is true, you can follow the poll updates and see how it changes here

Positive Trump polls are being given more weight right now because "unpredictability."

http://projects.fivethirtyeight.com/2016-election-forecast/updates/

[Dem2]

6. I guess that little bounce back we had today is gone then?

I had a feeling he would turn the gears behind the scene there to make sure that it didn't look like it was bouncing back.

[WillyBrandt]

7. I saw that too - his model is too clever by half: correlations and trends and uncertainty

My best guess is that his model tries to optimize and track a number of different factors:

(a) how is any given poll or state TRENDING - versus its absolute level
(b) how might a change in state A be revelatory about state B with similar demography (KY and TV, for example)
(c) how much uncertainty is implied by the polls (e.g. by # of polled who don't answer)

Individually each of these sort of seem reasonable, but I think his aggregate model has just gotten kind of weird and spits out illogical results by a sort of statistical rules-collision. So you get that crazy Utah change you saw.

I think Sam Wang's prediction is a bit too rosy, and NYT Upshot seems most reasonable to me. But Sam Wang is an exceedingly good explainer and very smart.

[Dem2]

8. You can't make this stuff up!! Look at this image I just captured!

His program has gone rogue!

[uponit7771]

9. WOW... WTF Silver !!! Is this the immediate tracking poll or the trend tracking poll? tia

[Dem2]

10. Polls only (default) though all 3 models are close to the same now.

[Persondem]

13. I wonder if there is a bug in his program concerning Utah

And whoa!! A +18 poll for VA dropped Clinton's chances!?!?!? WTF Nate!?!?

[Dem2]

14. Yeah, I think the 3rd party candidate in Utah has broken his program

This is the 3rd time a Utah poll with the expected result has hurt Hillary - it makes no sense unless the program can't deal with the missing vote in Utah and assumes there's a very high undecided vote there or something? He needs to fix this, he's looking like a fool lately.

[Buckeye_Democrat]

11. Michael Moore type of "reverse psychology" to inspire Democrats to vote?

It doesn't help, Nate! It's more discouraging, if anything!

I don't really believe that.

I think the problem is that he keeps including too many CRAP polls -- e.g., Remington -- assuming that the bias will all "balance out" in the end.

[0rganism]

12. in 538's defense, i could see it playing out thusly

for some time, Utah was in question for Mr. Trump, and not winning Utah would drop his overall chance to win considerably (probably 5%+, since he needs every formerly cherry-red state he can get to even have a chance of victory)

so today a poll comes out that shows he's very likely to win Utah, which re-opens a whole bunch of possible combinations to reach 270, even if its effect is discounted to reflect the unproven status of the pollster. this, in turn, improves his chances across the board.

i think it's legit in the context of Nate's model, and i'd still rather be on this side of the odds.

[Dem2]

15. Here's the problem with your theory

Trumps had it in the bag for a long time.

[0rganism]

16. lol i guess it's even *more* likely now

yeah i guess that idea's dead