Statement of Methodology
This survey of 500 likely Iowa Democratic Caucus voters was conducted between June 28 and July 1, 2019, and is based on a statewide random sample drawn from a list of registered Democratic voters who indicated they were very or somewhat likely to vote in their local Democratic Caucuses for president in eight months. Each of Iowa's five areas and demographic information were determined from past contested Democratic presidential caucuses using a probability-proportionate-to-size method, which means that the phone numbers assigned to each county were proportional to the number of likely caucus voters. Iowa's 99 counties were grouped into five general regions. The margin of sampling error for results based on the total sample is plus or minus 4.4 percentage points. Error margins increase for smaller subgroups in the cross-tabulation document which follows. All surveys may be subject to other sources of error, including, but not limited to coverage error and measurement error.