Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Hillygus and Jackman. 2003. Voter decision making in election 2000: Campaign effects, partisan activation, and the Clinton lega. AJPS 47: 583-96.
By looking at panel data using daily surveys during the 2000 campaign, we can see what kinds of voters are likely to switch vote choice, and when. Aggregate data (e.g. Johnston et al 2001) does not allow us to say 'who' is changing their mind, only that aggregate support for each candidate has changed.
Survey data conducted from a randomly selected panel frequently during the campaign season. Many responses every day. Panel effects are minimized because the panel answered only a few political questions mixed in with frequent marketing surveys.
Research on similar subjects