Editor's note: Michael Lieberman is founder and president of Multivariate Solutions, a New York research consulting firm.

Whenever presidential candidates give a campaign speech they are speaking to two different audiences: those who will vote for them and those who may or may not. These groups need different messages. Ardent supporters need reassurance, confirmation and an incitement to donate or become otherwise active. These messages often follow party lines. However, the voters on the fence have heard these platforms; they need something different, something that sways.

And from my experience working in political surveys, I can say that oftentimes the issues that will incite one group are not the same issues that will sway the other. Most elections, referendums or voter measures have two sets of drivers.

The first driving issue is what we’ll call the base. This is the underlying sales pitch of a campaign: what a candidate stands for, what a new referendum will accomplish or the basic reasoning behind a measure. The second driver consists of those attributes which may sway voters one way or the other. These are the issues that may move a voter who is very unlikely to vote for the measure to neutral, or a likely voter to the “very likely” column.

This article illustrates a commonly used survey structure that can identify both types of drivers. The poll we employ is no longer than a standard survey (in the field, time is money). Yet by strategically placing questions, we can uncover both the base and the sway – double the information – within the questionnaire length.

But before we can explain the solution, we first need to understand the problem. In this fictional example, our firm was contacted to identify the drivers behind a referendum to legalize gaming on the Oglala Sioux reservation in Pennington County, S.D.

The Oglala Sioux reservation is not far from both the Black Hills...