Chicago voters have 51 locations to choose from for early voting, while suburban Cook County voters can pick from 43 locations. Unike on Election Day, early voters are required to show a photo ID to cast a ballot.

WHERE TO VOTE EARY: Chicago, suburban Cook, DuPage, Will, Lake, McHenry, Kane, Kendall

Offices on the primary ballots include all members of the U.S. House and all members of the Illinois House and Senate. Republicans, of course, have a big presidential selection to make. 

Cook County voters pulling a Democratic ballot will also weigh in on two big countywide races. One is for clerk of the Circuit Court, with Chicago Ald. Rick Munoz (22nd) challenging incumbent Dorothy Brown. The other is for a seat on the Illinois Supreme Court, which has four Democrats running.

In the last presidential primary election, in 2008, about 300,000 Illinois voters cast their ballots early.

The popularity of early voting in recent years does have an impact on campaign strategy. Candidates looking for last-minute momentum may surge too late to win over people who’ve already voted.