If you’re a serious elections junkie you probably follow the work of Nate Silver and his colleagues at FiveThirtyEight. You might even check their primary forecast every few hours to see how the odds have or haven’t changed, as I did in the lead up to the 2016 general election. If you are that person, firstly may I say that you’ve picked something very cool and important to obsess over, so good job. Secondly, maybe it’s worth taking a bit of a break from the impressive but ultimately flawed work of polling aggregators like FiveThirtyEight and RealClearPolitics. Their outputs say that Joe Biden and Bernie Sanders are tied in Iowa. It’s not the most incorrect proposition ever, but it is needlessly under-confident. Sanders leads in Iowa. Here’s why the averages are misleading:

1. The variation in Iowa polls is not due to simple randomness but rather distinct methodological differences

When Monmouth University (A+ rated by FiveThirtyEight) finds Biden up six points in Iowa in the same two-week period that Selzer & Co (A+) find Sanders up three (with Biden in fourth place) and NYT/Siena (A+) find Sanders up seven, that’s not just due to sampling variation. What’s happening here, as expertly explained by NYT’s Nate Cohn is that Monmouth’s likely voter screen is excluding voters who say they’re likely to caucus but didn’t vote in recent primary elections or the 2018 general election. Selzer and Siena, on the other hand, rely more heavily on voters’ self-reported intent to vote. To illustrate this point, Cohn recently showed that under Monmouth’s methodology, Siena would’ve found Biden leading Sanders 24-23. One in five voters in the Siena poll did not pass Monmouth’s screen, and these voters backed Sanders over Biden 42-10. Sanders will win Iowa if a) these voters turn out as Siena/NYT expects them to and b) there is no late break against him. B) is an open question that we can’t predict very well and it’s why I can’t say for sure that Sanders will win, merely that he is the favorite to do so. But a) is a question we can meaningfully answer and should answer when it comes to predicting the winner. To Cohn’s credit, he does not say his findings are rock solid, he accepts with humility that pollsters such as Patrick Murray of Monmouth may be the ones in the right and he may be eating humble pie come February 3. I would go further, however. Cohn’s methodology IS the right path to take, regardless of whether Bernie actually ends up winning Iowa. Excluding (overwhelmingly young) voters who say they’re likely to caucus simply because they haven’t voted in previous primary or midterm elections – which are quite different to caucuses – is not good polling practice. That isn’t to say Monmouth isn’t a good pollster, they are and they have done amazing work in the last few years. But in this particular instance I am firmly on the side of Siena/NYT and therefore the only reasonable conclusion I can make is that Bernie Sanders has a robust lead over the field in Iowa.

2. Sanders has a strong positive trend

Whenever a new poll comes out in Iowa these days, like clockwork, Sanders is doing better than previously. I mentioned before that Monmouth University had Biden up six over Sanders in their early January poll – yesterday that lead was cut to two points. A recent Iowa State University poll showed Sanders at 24%, up from 21% a month ago. Suffolk University had him at 19%, up from 9% (!) in October. And Siena/NYT had him at 25%, up from 19% in November. It’s always good to head into the final week of an election with a positive trend line but it arguably matters even more in Iowa, where voters can often change their minds at the last minute, giving an unexpected boost to the candidate with the most ‘momentum’. In 2016, it was Marco Rubio who was on the up-and-up in Iowa polls – he was at 11% for most of December/January but surged to 16% in the final week. That momentum continued to caucus night and he ended up finishing a surprisingly close third with 23% of the vote. Or take the classic example of Rick Santorum in 2012; he burst from sixth place in the two weeks before the caucuses and increased his vote share in polls from just 6% to 16%. In the end he actually won Iowa – although by just 0.1% – despite polling six points behind eventually nominee Mitt Romney. This matters now because it seems Sanders is the only leading candidate with a clear positive trend, although perhaps not quite as strong as that of Santorum or Rubio. Biden, Buttigieg and Warren – all of whom could feasibly win the caucuses – are all flat or trending down. The only other candidate who could claim undeniable upwards momentum at this stage is Amy Klobuchar, but her gain is also Sanders’ gain, who would love it if she took more votes from Biden/Buttigieg. More on this in a bit.

So while Sanders’ raw position in the polls is good but not incredible, his trend line is something his campaign should be very happy with. Being in first place AND moving upwards with five days to go is a damn good combo.

3. Precinct thresholds may help Sanders (or: the Klobuchar singularity approaches)

The recent polls with the best data on this questions (Siena & Monmouth) are both in agreement; Sanders does better against Biden once candidates outside the top five (Biden/Sanders/Klobuchar/Warren/Buttigieg) have their choices re-allocated. Monmouth has the race going from Biden +2 to a TIE in a six-way race (the five + Yang) and would presumably show a Sanders lead of ~2 if Yang’s choices were re-allocated too. Meanwhile Siena has the race at Sanders +7 both on the ballot with all the candidates and the four-way ballot (five minus Klobuchar). If Klobuchar were still in the running, it seems likely Sanders would extend his lead out to ten points in the Siena poll.

This matters in Iowa in particular because each precinct has a viability threshold of at least 15% so if your candidate cannot reach that threshold, they get no votes (a.k.a State Delegate Equivalents) from that precinct. As candidates such as Yang and Steyer will likely reach 15% in very few precincts, if any, the second choice intentions of their supporters are important. While Sanders seems to benefit from picking up Steyer/Yang/Gabbard supporters, his major weak point is Klobuchar. By all accounts, he’d be lucky to pick up 10% of Klobuchar voters in precincts where she’s not viable, whereas Biden might be earning a majority of those voters. This means Sanders has got to hope Klobuchar is viable in as many precincts as possible, to cut into Biden’s support. The good news for the Sanders camp is that this seems to be materializing. Recent polls show Klobuchar gaining statewide, garnering around 10% of the vote. And new crosstabs from none other than Nate Cohn confirm what seems intuitive – Klobuchar’s voters are disproportionately clustered in certain precincts such that she will reach 15% in many of them even if she falls short statewide. His Siena/NYT poll had Klobuchar doing nearly twice as well in Clinton ’16 precincts (11%) than Sanders ’16 precincts (6%). If I had to guess I’d say Klobuchar ends up being viable in 20-40% of precincts – not exactly the late surge the Sanders campaign would love but enough that she can be a thorn in Biden’s side.

At the same time, Warren being non-viable in a lot of precincts could also give the Sanders campaign a boost – not that it necessarily needs one. Recent polls show her hovering at around 15% statewide, enough to be viable in most precincts once undecided voters have been allocated. However it still seems likely she will miss out on viability in a number of precincts – particularly rural or conservative ones. Just as Klobuchar is on the cusp of viability in precincts that voted for Clinton in the 2016 caucus, Warren is in the danger zone of non-viability in these precincts, getting just 12% there. This too helps Sanders because he is the clear second choice of Warren voters, although he likely won’t earn a majority of their votes. Warren being non-viable in 20-40% of precincts could give Sanders a boost of maybe one percentage point, and that’s nothing to scoff at in a close race.

Finally, Sanders benefits from having quite well distributed support around the state such that he is unlikely to fail to reach the 15% threshold in many precincts. In the Siena poll he is at 31% in Sanders ’16 precincts and at 23% in Clinton ’16 precincts. He gets at least 19% in all four ‘regions’ of Iowa. Admittedly he only gets 9% of the 65+ voter demographic but luckily that group doesn’t cluster in the same way youth do around universities. There won’t be many precincts where 65+ voters are a majority. Biden on the other hand, only cracks 15% with 65+ voters and is at just 10% with 18-29 year olds. Those numbers lead me to believe he will almost certainly be non-viable in a few precincts in liberal strongholds where Sanders did well in 2016 such as Iowa City and Fairfield.

Sanders is the likeliest candidate to winIowa no matter what weird stuff happens with precinct viability, owing to his current polling lead, enthusiastic base and upwards momentum. Even in a world where Klobuchar is completely non-viable and Biden/Warren/Buttigieg are completely viable, he maintains a 7-pt lead per Siena. But it seems to me that the current dynamic lends him even more strength, as the moderates candidates split the field in their scramble to stop him, blinded by their own desire to be President and inability to understand just what draws voters to Bernie Sanders. Klobuchar shares a lot more in common ideologically and strategy-wise with Biden than with Sanders but she may just end up handing Iowa to Bernie just s Michael Bloomberg might hand a state like Texas to the Vermont Senator on Super Tuesday. Everyone in the race really truly believes they should be President and for that reason there isn’t really going to be a concerted effort to stop Sanders. If anything, Biden losses in Iowa and New Hampshire might cement the idea that he can’t stop Sanders, pushing even more voters towards a moderate alternative (Bloomberg, Klobuchar, Buttigieg, Bennet? who the fuck knows, let’s wait for the next Jonathan Chait op-ed to inform us). Ironically, this would probably only bolster Sanders’ campaign as we head into the delegate-rich primaries of March and April. But I’m getting ahead of myself. The point is; the conditions in Iowa are ripe for a Bernie Sanders victory. Don’t kid yourself into thinking it’s a tossup just cause Nate Silver says so.