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89 Different Scenarios For What Things Could Look Like After Iowa

Maybe you’ve seen articles elsewhere detailing the three or four most likely post-Iowa scenarios, full of elegantly-constructed narratives about how the race might unfold.

This article … is not going to be like that. Rather, it’s just going to be a bunch of rather detailed tables generated by our forecast model, outlining what the Democratic nomination race could look like given the order candidates finish in Iowa and the margins of victory. We hope they’re useful for detail-oriented readers over the course of the evening.

First up: Here’s a table showing the post-Iowa odds a candidate has of winning a national delegate majority given who won Iowa and his or her margin of victory. Specifically, we’re defining a “narrow” win as anything less than 4 percentage points over the second-place candidate, a “medium” win as 4 to 12 percentage points, and a “large” win as more than 12 percentage points. We haven’t listed scenarios if they occurred less than 0.5 percent of the time (at least 50 out of 10,000 simulations) in our final model run. Keep in mind that there is some noise in these numbers; we’ll run a full set of simulations late Monday night or Tuesday morning once we have the caucus results.

How Iowa’s results will affect the nomination odds, Part I

Based on winner and margin of victory

chance of winning the majority of delegates overall
Winner
Margin
Biden
Sanders
Warren
Buttigieg
Other
None
Biden large 84% 6% 2% 0% 0% 7%
Biden medium 75 11 2 1 0 11
Biden narrow 71 13 2 1 0 12
Buttigieg large 25 12 1 34 0 28
Buttigieg medium 33 14 5 20 0 28
Buttigieg narrow 36 20 4 15 0 25
Klobuchar medium 38 21 3 2 11 24
Klobuchar narrow 36 28 7 1 7 21
Sanders large 17 67 2 0 0 14
Sanders medium 25 55 2 0 0 17
Sanders narrow 32 46 2 1 0 18
Warren large 19 9 43 1 0 29
Warren medium 32 9 33 1 0 24
Warren narrow 32 16 24 2 0 26

Specifically, we’re defining a “narrow” win as anything less than 4 percentage points over the second-place candidate, a “medium” win as 4 to 12 percentage points, and a “large” win as more than 12 percentage points. Scenarios are only listed if they had at least an 0.5 percent chance of occurring.

The most definitive outcome of the night — albeit a somewhat unlikely one — would be a Joe Biden landslide, which would put his majority chances at 84 percent. Even a narrow Biden win would leave his opponents in fairly bad shape, though.

For a Bernie Sanders win, the margin matters a bit more. A medium-to-large Sanders win could boost his chances of winning the delegate majority to above 50 percent. A narrow win might leave him as the front-runner, but would keep things more competitive.

Wins by candidates other than Biden or Sanders — meaning, Elizbeth Warren, Pete Buttigieg or Amy Klobuchar — would scramble the picture, significantly increasing the chance of no one winning a delegate majority, possibly meaning a contested convention. Of course, any of these candidates winning Iowa would also massively improve their own chances overall. But they’re far enough behind in other states that they’d still have some work to do. For instance, a medium-sized Warren win would give her about a 1-in-3 chance of winning the majority, with Biden also at 1-in-3 and Sanders’s chances significantly diminished but not hopeless.

To add a layer of complication, here’s what you get if you specify the margin of victory and also who the second-place candidate is:

How Iowa’s results will affect the nomination odds, Part II

Based on winner, margin of victory and second-place candidate

chance of winning the majority of delegates overall
winner
margin
2nd
Biden
Sanders
Warren
Buttigieg
Other
None
Biden large Buttigieg 87% 6% 1% 0% 0% 6%
Biden large Klobuchar 80 8 2 0 0 11
Biden large Sanders 84 6 2 1 0 7
Biden large Warren 82 4 5 0 0 8
Biden medium Buttigieg 78 8 2 2 0 11
Biden medium Klobuchar 77 13 3 2 0 5
Biden medium Sanders 75 14 1 0 0 10
Biden medium Warren 74 6 4 0 0 16
Biden narrow Buttigieg 74 8 2 4 0 13
Biden narrow Sanders 72 16 1 0 0 10
Biden narrow Warren 66 8 8 0 0 18
Buttigieg large Biden 34 8 1 30 0 27
Buttigieg large Sanders 17 16 2 34 1 31
Buttigieg large Warren 24 10 0 37 0 29
Buttigieg medium Biden 41 9 4 17 0 28
Buttigieg medium Sanders 30 19 3 19 0 29
Buttigieg medium Warren 30 10 9 26 0 25
Buttigieg narrow Biden 51 13 2 15 0 20
Buttigieg narrow Sanders 27 28 4 15 1 26
Buttigieg narrow Warren 21 16 12 18 0 33
Sanders large Biden 21 64 2 1 0 13
Sanders large Buttigieg 15 71 1 0 0 13
Sanders large Klobuchar 11 69 0 0 1 19
Sanders large Warren 11 69 3 0 0 17
Sanders medium Biden 29 53 2 0 0 14
Sanders medium Buttigieg 20 59 1 1 0 20
Sanders medium Klobuchar 20 59 0 0 0 20
Sanders medium Warren 23 50 5 0 0 22
Sanders narrow Biden 37 44 2 0 0 17
Sanders narrow Buttigieg 26 48 1 3 0 21
Sanders narrow Klobuchar 34 48 0 0 0 17
Sanders narrow Warren 24 51 6 0 0 19
Warren large Biden 25 4 48 1 0 22
Warren large Sanders 12 16 40 0 0 32
Warren medium Biden 40 7 31 1 0 21
Warren medium Buttigieg 15 8 43 4 0 30
Warren medium Sanders 33 10 31 1 0 24
Warren narrow Biden 44 11 21 0 0 24
Warren narrow Buttigieg 30 10 23 8 0 28
Warren narrow Sanders 25 24 24 1 0 26

Specifically, we’re defining a “narrow” win as anything less than 4 percentage points over the second-place candidate, a “medium” win as 4 to 12 percentage points, and a “large” win as more than 12 percentage points. Scenarios are only listed if they had at least an 0.5 percent chance of occurring.

You can see that Sanders and Biden generally wouldn’t mind if Buttigieg or Klobuchar finished in second place, as they are the furthest behind in national polls.

Another fun scenario from the table is what happens if the polls are exactly right, resulting in a narrow Sanders victory with Biden in second place. That would make Sanders the front-runner overall, but not by much, with a 44 percent chance versus 37 percent for Biden.

Buttigieg and Warren finishing first and second in some order would produce the most chaotic outcomes, with at least four candidates still having a plausible shot at the nomination and the “no majority” scenario also still very possible.

Finally, here is a chart showing post-Iowa outcomes based on the order of finish of the top three candidates. I’m going to drop the margin of victory criteria for this one since that produces too many scenarios to keep track of.

How Iowa’s results will affect the nomination odds, Part III

Based on winner, second and third place candidate

chance of winning the majority of delegates overall
winner
2nd
3rd
Biden
sanders
warren
buttigieg
Other
None
Biden Buttigieg Klobuchar 83% 5% 0% 1% 0% 11%
Biden Buttigieg Sanders 80 9 1 2 0 9
Biden Buttigieg Warren 79 4 3 2 0 12
Biden Klobuchar Sanders 72 10 3 1 0 14
Biden Sanders Buttigieg 77 13 1 1 0 8
Biden Sanders Klobuchar 73 15 0 0 1 9
Biden Sanders Warren 78 9 2 0 0 10
Biden Warren Buttigieg 77 4 6 1 0 12
Biden Warren Klobuchar 76 4 4 0 0 16
Biden Warren Sanders 73 6 6 0 0 14
Buttigieg Biden Sanders 43 11 2 18 0 26
Buttigieg Biden Warren 42 10 4 19 0 25
Buttigieg Sanders Biden 30 20 2 19 1 28
Buttigieg Sanders Klobuchar 19 19 4 28 0 30
Buttigieg Sanders Warren 17 24 5 26 0 29
Buttigieg Warren Biden 24 7 12 30 0 28
Buttigieg Warren Sanders 28 16 5 21 0 30
Sanders Biden Buttigieg 30 54 1 1 0 14
Sanders Biden Klobuchar 26 56 2 1 1 15
Sanders Biden Warren 27 56 2 0 0 14
Sanders Buttigieg Biden 23 59 1 2 0 16
Sanders Buttigieg Klobuchar 13 67 0 1 0 19
Sanders Buttigieg Warren 16 64 2 0 0 19
Sanders Klobuchar Biden 21 62 0 0 1 17
Sanders Klobuchar Buttigieg 19 66 0 0 0 14
Sanders Klobuchar Warren 16 54 0 0 0 30
Sanders Warren Biden 20 58 4 1 0 17
Sanders Warren Buttigieg 15 57 5 0 0 23
Sanders Warren Klobuchar 17 62 5 0 0 16
Warren Biden Buttigieg 42 5 31 1 0 21
Warren Biden Sanders 37 9 31 0 0 22
Warren Buttigieg Biden 27 9 30 3 0 30
Warren Buttigieg Sanders 14 10 43 5 0 29
Warren Sanders Biden 25 15 32 0 0 28
Warren Sanders Buttigieg 27 19 28 1 0 26

Scenarios are only listed if they had at least an 0.5 percent chance of occurring.

This isn’t uncovering too much that you couldn’t have gleaned from the other charts, but note that Biden’s chances could fall to as low as 13 percent in some scenarios if he finishes outside the top 3.

Also note that the model thinks Buttigieg and Klobuchar really need a win outright, as they remain far behind the front-runners in national polls. Finishing a solid second in Iowa might leave open some possibility of their winning the nomination after a long slog, perhaps at a contested convention. But it would make winning via the majority route hard. Warren is slightly more viable with second-place finishes, however, especially if Buttigieg is the winner.

Nate Silver is the founder and editor in chief of FiveThirtyEight.

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