Join us for the latest edition of the RealClearPolitics podcast "Poll Position." On this program, RCP president and co-founder Tom Bevan discusses the results of the Iowa caucuses with J. Ann Selzer, president of Selzer & Co and conductor of The Des Moines Register/NBC News/Mediacom Iowa Poll. Topics include the reasons for Trump's margin of victory, the challenge of polling caucus goers, the effects of turnout and the shift toward the Republican Party in Iowa over the last 10 years. Each week, RCP's "Poll Postion" looks at the state of American political polling and features in-depth discussions with Americas top pollsters and public opinion experts.