Yesterday, I started going through the current state of the electoral map, and talked about the fact that there are a bunch of plausible paths for Clinton to get to the magic number of 270 electoral votes, and implicitly, that there are very few ways for Trump to get that magic number. What I didn't do was put a probability on Clinton going over the top. Plenty of people try to compute that. Anyone doing so is playing fast and loose with the math. Here's why.
Imagine Clinton has a 75% chance of winning Colorado and a 75% of winning New Hampshire (a plausible method of getting a majority in the electoral college, as I showed yesterday). Well, that's simple, right? .75*.75=.5625. Clinton would have a 56.25% chance of winning both, right? Not so fast. That computation is based on the premise that winning Colorado and New Hampshire are "independent events." That would mean winning one's got nothin' to do with the other. That ain't so. There are nationwide factors. But, there are local factors too. Colorado has more Latinos than New Hampshire. That will help Clinton more in CO than NH. So, how do we calculate the "joint probability" of Clinton winning both CO and NH? We need to know exactly how independent the events are. Do we? Fuck no. Plenty of people have guesses, and through those guesses, they compute probabilities of victory in the electoral college for Clinton and Trump, but those are based on imputed levels of independence for the state contests, and that's all pulled from the statistician's head, which is generally up his ass, so it's actually pulled from the statistician's ass in a whole, rectal haberdashery thing.
Your best guess for any one state is always whoever is ahead in the polling average in that state. Trying to get more precise than that is a fool's errand at this point, and trying to compute joint probabilities across states is a con. Don't be a rube.
What can we do? We can look at scenarios. That's what I did yesterday. There are more plausible scenarios for Clinton. The polls favor Clinton. If every state goes the way their current polls say, Clinton will win. Default guess right now, Clinton.
How confident can we be? Fuck if I know. This year is nuts. Just remember: Trump needs to run the table. Clinton can lose a bunch of swing states and still take the White House. That's why the odds favor Clinton by some small amount. Right now, PredictWise gives Clinton around a 72% chance of winning, which is higher than the poll aggregators. That is probably based on a run-the-table line of reasoning, but at this point, one is on solid footing by defaulting to uncertainty anyway.
This year is nuts.