Low turnout among a key cog in the Democratic coalition - young voters - will likely hurt Democrats in November, which is why Democrats like Illinois Senator Dick Durbin are beating the drum on the issues of student loans, tuition costs, textbook fees, and minimum wage.
According to the left-leaning Rasmussen polling, since the first national exit poll was taken for a midterm election in 1978, only once (in that first survey) has the 18-to-29 age group made up a larger portion of a midterm electorate than voters who were 60 or older. And not only have young people almost always been the smallest part of midterm electorates in this period, their participation has usually been much smaller compared to presidential years. (see below)
As a result, Durbin, Quinn and other Dems have been selling feel-good ideas like free textbooks, student loan forgiveness, and increased minimum wage.
Age composition of electorate in presidential and midterm elections, 1972-2010 exit polls