[W]e shouldn't trust any single model, or even a single average of the various models. Instead, the best way to read all of this is to focus on the range, both in individual models when supplied by the authors, and across models. That's going to give smart readers uncertainty, and that's exactly what we all should be experiencing right now. [...] [F]or now, the right attitude isn't to try to figure out which model to trust; it's that we're better off the more we know, and each reasonable model adds to our general sense of how things are going.
The real drama this election cycle is focused almost entirely on one institution: the U.S. Senate. The Democratic caucus has a five-seat majority -- a majority status it's enjoyed for a decade -- and a net gain of six seats would give Republicans control. Is that likely to happen? It's a distinct possibility. How likely is it?
That depends on which measurement you're inclined to believe.
There was a day last week in which a New York Times analysis gave Republicans a 65% chance of winning the Senate majority, while Sam Wang's analysis at the Princeton Election Consortium gave Democrats a 70% chance of keeping their majority. Both reports were based on reliable data, both used credible statistical models, and both were prepared by credible professionals.
The Upshot has a table that shows six competing Senate forecasts, and there's a fair amount of disagreement among them. It doesn't include the Daily Kos model, which is also good, and yesterday Huffington Post entered the fray with a forecast model of its own.
Clarity, however, remains elusive. Today, the New York Times' latest forecast gives Republicans a 66% chance of being in the majority, while the Huffington Post's latest forecast gives Democrats a 57% chance of being in the majority.
Jonathan Bernstein is asking the same question on the minds of many: which is the most trustworthy forecast?
That sounds about right to me. None of the forecast models can be dismissed as "wrong," necessarily, and all of the models can tell the public something useful, even when they disagree.
Some of these forecasts are based exclusively on available polling data. Others take "fundamentals" into consideration (fundraising, district characteristics, national trends, etc.). Both approaches have merit, though they obviously lead to significant differences in results.
And perhaps most strikingly, the forecasts differ so greatly because there are so many competitive contests that will dictate the outcome. Minor fluctuations in a few races end up having a significant impact, making some of the forecasts pretty sensitive.
So, looking ahead, keep a few things in mind. There are three seats currently held by Democrats that are likely to flip to Republicans (South Dakota, West Virginia, and Montana). There are a couple of seats currently held by Republicans where the GOP candidate is the clear favorite, but the parties are keeping an eye on them, unsure of the outcome (Kansas and Mississippi).
There are a couple more seats currently held by Republicans where the GOP candidate is ahead, but Dems see a real opportunity (Kentucky and Georgia). There's at least one seat currently held by a Democrat, but where Republicans think there's a slight chance of success (New Hampshire).
And then there are the toss-ups (Alaska, Arkansas, Colorado, Iowa, Louisiana, Michigan, and North Carolina).
If you've been waiting until after Labor Day to start taking the cycle seriously, time's up.