In case there was any doubt that the youth vote could hurt Democrats in 2014, the following two charts should just about kill it.

The data below come from Democratic pollster Paul Harstad, who conducted a survey of young voters for the Youth Engagement Fund and Project New America. It looks in-depth at what motivates young voters -- specifically, millennials aged 18 to 31 -- to vote, and to vote Democratic.

The first chart looks only at those young voters who cast ballots for President Obama in 2012:

What's most notable here: Only half of young people who voted for Obama say there is even a chance that they'll vote in 2014 and that their vote would be for Democrats.

Only 30 percent of young people who voted for Obama in 2012 say that they will "definitely" vote for a Democrat for Congress in 2014, and only another 7 percent say they will "probably" vote for Democrats. The remaining 13 percent are "iffy."

Here's another way to look at this:

While millennials voted for Obama 63 percent to 33 percent in 2012 -- a 30-point margin -- they are significantly less Democratic-leaning heading into the 2014 election.

These numbers actually look a lot like they did four years ago. While young voters favored Obama by 34 points in 2008, they tilted in Democrats' favor by just 16 points in 2010 -- about half the margin. This poll suggests Obama's margin will drop from 30 points in 2012 to around 15 points in 2014 -- again, about half the margin.

A repeat of 2010, of course, is not quite what Democrats are hoping for this year.