Here are the two best clues for who will win Iowa: 18% and 28%. In 2016, Hillary barely beat Bernie 49.9% to 46.6%. Voters aged 18-29 were 18% of the electorate and they went for Bernie 84-14. If young voters are more than 18% of the electorate this year, it’s good for Bernie.
In 2016, 28% of the Iowa electorate said they were “very liberal”. Those voters went for Bernie 58-39. If very liberal voters are more than 28% this year, it’s good for Bernie.
One other factor: Turnout was 236,000 in 2008 (Hillary vs Obama). Turnout was 171,000 in 2016 (Hillary vs Bernie). Bernie, with the support of young voters who don’t turn out at the same rate as seniors, benefits from a higher overall turnout.
