Open Structure to Influence Ohio Primary Outcome?

The political chatter class is abuzz about today’s two Republican winner take all primaries — Florida and Ohio — that will pit Republican front runner Donald Trump against those two states’ hometown candidates, Marco Rubio and John Kasich, respectively.

Florida’s primary is closed, meaning only registered Republicans are allowed to cast a ballot for a Republican candidate; Ohio’s primary, on the other hand,  is open to registered Republicans and independents, but not to registered Democrats.

Last week, Ash wrote about the correlation between which candidate emerged from the contest as victor and whether a primary or caucus was open or closed.

What he found was this: As of the time publication, March 7th, Donald Trump had won a dozen state primaries or caucuses. Of those twelve contests, nine were open and only three were closed. Ted Cruz, on the other hand, as of March 7th, had won a half dozen state primaries or caucuses. Of those six, all but one was closed. (The one open contest that Cruz won, Texas, is his home state.)

The outcomes are summarized in the two tables below:



What — if anything — does this mean for today’s two true winner take all state primaries in Florida and Ohio?

We did a back of the envelope calculation, carrying through Donald Trump’s past performance, in both open and closed contests, in an attempt to evaluate whether primary structure (open v. closed) might have any impact on today’s Florida and Ohio primaries.


Let’s first take a look at Ohio.

The Real Clear Politics poll-of-polls average has Ohio Governor John Kasich leading in the state by +3.4 points.


Of the six recent polls used to create the RCP average, three polls have Kasich ahead while two have Trump tied with Kasich. The widest margin of victory Kasich has is +6 points. (The smallest Margin of Error within the constituent polls used to create the RCP average is 3.7 points.)

We suspect, based on Trump’s past performance in open contests, that the Ohio race may be closer than the polling data suggests — possibly a dead heat — which could put Ohio’s 66 primary delegates within Trump’s grasp.

Donald Trump has won a total of 41% of delegates in all proportional states to date, regardless of whether the contest was open or closed. In closed states, however, Trump won only 35% of votes in proportional states, compared to Ted Cruz’s 42%. In open states Trump won 44% of votes in proportional states, while Ted Cruz has won only 34%. (See table & bar graph below.)



Because proportional delegate allocation serves as a proxy for total voting in proportional representation states, we believe that it is possible, based on past performance that Donald Trump may receive up to a +3% advantage, compared to his average outcome in early contests.

Adjusting Donald Trump’s RCP polling average up 3% higher would put Ohio in a statistical dead heat.



Turning briefly to Florida — where Trump maintains a double digit lead in the Real Clear Politics poll-of-polls:


In Florida, unlike Ohio with its razor thin margins, Trump’s double digit spreads seem far beyond the relatively modest effects of open / closed contest variability.



Ash Bennington is Editor-in-chief of EconoMonitor.

Mark Skinner trained as a data scientist and works as a Country Insights Analyst at Roubini Global Economics.


Source Data


Data source: Election 2016 — Republican Delegate Count