The CBS News 2016 Battleground Tracker is a panel study based on interviews conducted on the internet of registered voters in California, Florida, Georgia, Illinois, Iowa, Michigan, New Hampshire, New York, Ohio, Pennsylvania, South Carolina, Texas, Virginia, and Wisconsin. The poll was conducted by YouGov, an online polling organization.

The first wave was fielded between September 3-10, 2015, with 4860 respondents, and the second wave fieldwork was completed between October 15-22, 2015, with 3,952 respondents and the third wave between November 15-19, 2015. The fourth wave was fielded between December 13-17, 2015. The majority of the 2nd-4th wave respondents are recontacted panelists. The first 4 waves consist of interviews in Iowa, New Hampshire, and South Carolina only. The fifth wave added new interviews in Florida, Georgia, and Texas, and was completed between January 17-21, 2016. The sixth wave was fielded only in South Carolina, with interviews completed February 10-12, 2016. The seventh wave was fielded also in February, among panelists in Georgia, Texas, and Virginia. The eighth wave fielded February 22-26, 2016, and recontacted panelists from the January wave in Georgia and Texas. Virginia respondents were all new to the panel. The nineth wave was fielded to new respondents in Michigan from March 2-4, 2016, and in addition, respondents in Florida, Illinois, and Ohio were contacted March 9-11, 2016. Respondents in New York, Pennsylvania, and Wisconsin were contacted March 29-April 1, 2016 for the tenth wave. In the eleventh wave of our primary surveys, respondents in California, New York, and Pennsylvania were contacted April 13-15, 2016.

Respondents were selected from YouGovs and two other online panels. These are “opt-in” panels which are open for anyone to join. However, YouGov also randomly selected persons from voter registration lists who had previously voted in primary elections and contacted them by phone. A total of 24,017 registered voters were contacted by phone and the YouGov sample includes 1,821 phone recruits.