The Fix last week looked at just how important the youth vote will be in 2014, as many of the key states holding Senate races had higher-than-average youth turnout in 2012. That means there is plenty of room for dropoff among young voters -- and plenty of reason for concern among Democrats, who count them as a vital part of the so-called "Obama coalition."

A new poll from Harvard University's Institute of Politics should give Democrats plenty of reason for concern on that front.

That's because young voters aren't just much less likely to vote than they were in 2012; they're also significantly less likely to vote than they were in 2010, when Democrats got their clocks cleaned.

While 31 percent of young people (defined as 18 to 29 years old) said they were definitely going to vote in February 2010, just 23 percent say the same in April 2014.

Not only did Democrats lose big in 2010; youth turnout in that election was down hugely from 2008 and one of the worst years on record. Should this lack of enthusiasm persist, youth turnout could be historically low in 2014.

This demographic is generally Democrats' best age group, with Obama carrying it by more than 20 points in 2012 and more than 30 points in 2010. If young people don't turn out to vote in 2014, that means Democrats will have to try and gain those votes elsewhere.

It could also hurt Democrats even more than the numbers above might suggest. That's because 32 percent of conservative young people say they're likely vote, compared to just 22 percent of liberal young people.

Now, young people alone aren't going to sink Democrats in 2014. But this lack of enthusiasm exists in several other key parts of the Obama coalition, including African Americans, Latinos and unmarried women -- something Obama himself has acknowledged. And the combination of those groups could prove lethal.

Democrats need the electorate to be better for them than in 2010; not worse.