Gallup reports that Democrats have an edge with the young:

Gallup Daily tracking data reinforce the value of younger voters for the Democrats, showing that 18- to 29-year-olds favor the Democratic candidate over the Republican candidate in their local districts by a 12-point margin. In contrast, the Republican candidate is on top among all groups of voters aged 30 and older.

But lower turnout potentially diminishes the value of that advantage:

Younger voters remain less enthusiastic about voting in this year's midterm elections than those who are older, underscoring the challenge facing the Democratic Party in its efforts to re-energize these voters, who helped President Obama win the presidency in 2008.

Lower youth turnout is consistent with historical patterns. As we discuss in our chapter on public opinion and political participation, young people have long voted at lower rates than older people. Here are the turnout rates by age for citizens in the 2008 election:

18-24 48.5%

25-44 60.0%

45-64 69.2%

65+ 70.3%