ADVERTISEMENT Hillary Clinton, meanwhile, polls very poorly in the age group. The most recent Harvard Institute of Politics (IoP) poll of young voters showed her holding just a 37% approval rating among millennials, compared with a 53% disapproval rating. After Bernie Sanders endorsed Hillary Clinton, nearly half of his millennial supporters said they would vote third-party instead of Hillary Clinton.

That's very troubling news indeed for the Democratic Party. Young voters are not necessarily flocking to Donald Trump, but they are nevertheless rejecting the presumptive Democratic nominee. The Democratic Party missed the opportunity to win a generation of voters, which is a shame considering the profound effect that Sen. Sanders has had in shaping the opinions of young Americans.

In the survey conducted by the Harvard IoP examining the attitudes of young voters, there was a marked difference in voter attitudes over the course of just a single year. For example, from 2015 to 2016, the number of young voters supporting universal healthcare increased from 45% to 48%. The number of young voters that believe the government should do more to address poverty increased from 40% to 45%. For the first time in five years, there were more young people that identified as Democrats than independents. Only 22% of young people identified as Republican.

Although these differences may seem negligible, a 3% shift in public opinion over the course of just a single year is nothing short of significant, especially when elections are often decided by a matter of just a few percentage points.

Why does this happen?

As it turns out, people often change their political positions to match the politicians that they like and support. Essentially, the messenger is often more important than the message itself.

In one study, researchers proposed a policy to subjects. One group was told that George Bush supported the policy, while another group was told that Nelson Mandela supported the policy. A third group, the control group, did not have anyone supporting the policy. The subjects in this study generally held an unfavorable view of Bush, but a very favorable view of Mandela.

The study found that if the policy is presented by an unpopular figure, Bush, the favorability of the policy was 10% lower than the control group's. Meanwhile, if the figure was well liked, the policy's favorability would be 5% higher than the control group's. This amounted to a net 15% favorability difference for the same policy, though presented by different public figures.

Had the Democratic Party nominated Sen. Sanders, a figure was astronomical approval ratings among millennials, the party could have actively shaped how the entire generation viewed Democratic policy.

Instead, the party chose to nominate a figure with a tanking approval rating in the age group, and is likely to view her negatively, as well as her policy negatively as a result.