In 2012, the number of 18-to-29-year-old voters dropped by 1.8 million from the previous presidential election year. “It seems likely that the observed young-adult voting surge of 2004–2008 was temporary,” a U.S. Census study concluded, “and not representative of a permanent shift towards greater young-adult engagement in presidential elections.”
In 2016, this is likely to affect Clinton’s performance in several college-heavy states that have had relatively high turnout—and high Democratic voting rates—among those age groups. That includes swing states such as Iowa, North Carolina, New Hampshire and Virginia. Just look at what happened in the past cycle. In Iowa, for example, 18-to-29-year-olds dropped from 17 percent of the 2008 vote to 15 percent in 2012—and were less likely to vote for Obama. The result was a net loss of close to 30,000 votes, in a contest Romney lost by less than 90,000 votes.
And that was with Obama, who did far better than Clinton with young voters.
During primary season, Sanders took a stunning 84 percent of the under-30 vote in the Iowa caucuses. Many of these young Sanders voters may come around to support Clinton over Trump in the general—just as Clinton’s bitter supporters eventually came to support Obama in 2008. The question is, though: How many?
Maybe not enough. As Jennifer Duffy of the Cook Political Report notes, there is a big difference between 2008 and 2016: Then, Clinton’s so-called PUMA die-hards were mostly middle-age suburban women, with long-standing ties to the Democratic Party. In other words: likely voters. Most young Sanders voters, on the other hand, are not yet regular voters, and certainly not the kind of committed Democrats Clinton can count on; her campaign will need a significant get-out-the-vote effort to persuade them to show up in November. That will be more difficult the more she takes the conservative path, pivoting to the center for the general election, and focusing on messages geared toward her core—older—voters. How Hillary Clinton Loses to Donald Trump - POLITICO Magazine