Turnout was simply dreadful, the lowest in many people's lifetime. 

Turnout was low across the state. In Sangamon County, a Republican stronghold in central Illinois, about 1 in 5 registered voters cast ballots. The numbers were about the same in the GOP-leaning suburbs of Cook County. Kane County saw similar results, although officials said turnout among Republicans topped 50 percent.

The city of Chicago, overwhelmingly Democratic, might end up with its lowest turnout since World War II. Officials said turnout was 22.8 percent, with just 1 percent of precincts left to count as of early Wednesday morning.

The previous Illinois low for primary turnout was just two years ago.  There was no statewide race this year but everyone in the congressional delegation and state legislature has a new district to defend and there were some very hotly contested races that had local organizations working to get out the vote.  

Admittedly many Illinois voters are post party politics after decades of corruption by Democrat and Republican alike but this low of turnout is not a healthy sign.  Low turnout tends to means one of two things. Sometimes low turnout means people are pretty content with the status quo and see no reason to rock the boat. Other times low turnout means voters are deeply unhappy with both political parties and see little difference in the options before them.  Each alternative strongly favors the incumbent.