CHICAGO (CBS) — Polls have opened for the primary election in Illinois, and officials are expecting a busy day in the Chicago area, with heated battles on the ballot for both Democrats and Republicans.

While Hillary Clinton once held a commanding lead in the race for the Democratic nomination for president, it’s now a neck-and-neck contest with Bernie Sanders. Donald Trump leads the Republican field in the race for president, but Ted Cruz is within striking distance.

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The race for president isn’t the only hot contest on the ballot in Illinois. Embattled Cook County State’s Attorney Anita Alvarez faces opposition from two opponents in the Democratic primary, in the wake of the Laquan McDonald scandal. Challengers Donna More and Kim Foxx both have blasted Alvarez for waiting more than a year to file murder charges against the Chicago police officer who shot McDonald 16 times, but Alvarez has defended her handling of the case, saying her office conducted a thorough investigation.

Meantime, a state legislative race is serving as a proxy war between Illinois House Speaker Michael Madigan and Gov. Bruce Rauner, with Rep. Ken Dunkin (D-Chicago) facing a challenge from rookie candidate Juliana Stratton. Dunkin has repeatedly sided with Rauner on key votes in Springfield, and allies of Rauner and Madigan have spent millions on the race. President Barack Obama even made the unprecedented move of weighing in on a Democratic primary in his home state, backing Stratton after chiding Dunkin last month during a speech on the value of bipartisan cooperation. Dunkin had run ads making it seem like Obama was endorsing him, so Obama has now run ads endorsing Stratton.

Cook County election officials have said they expect strong turnout for the primary, likely better than 43 percent. The last time local election officials saw turnout that high for a primary was 2008, when Barack Obama was running for president.

Already, the county has seen a record number of early votes, with 230,000 ballots already cast in Chicago and the Cook County suburbs. Cook County Clerk David Orr said this primary generated a record number of mail ballots and grace period registration, with a large number of young voters.

If you’re 17, but you’ll turn 18 by the general election in November, you’re eligible to vote in the Illinois primary.

A couple helpful reminders; you can bring a cheat sheet with you into the polling place if you need to write down the names of some candidates you want to vote for (or against), but you cannot bring in political signs or other materials that could influence voters.

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“Campaigning is not allowed within 100 feet of a polling place. Even wearing buttons or a T-shirt for a particular candidate is considered to be campaigning,” Chicago Board of Election Commissioners Chair Marisel Hernandez said.

The Illinois Attorney General’s office has said 179 teams of assistant attorneys general and investigators will be monitoring Tuesday’s election.

The city will have even more investigators in the field.

“We will have 500 investigators throughout the city, so we’ll be roving from precinct to precinct. Others will be on call; in case there’s any issues, they will go there immediately,” Hernandez said.

Orr said, with improved technology, he’s hoping things run smoothly at the polls.

If you have a flexible schedule to go out and vote, Orr said 9 a.m. to 3 p.m. is the time you’re least likely to run into crowds. Polls opened at 6 a.m., and close at 7 p.m.

A few irregularities were reported in the first few hours of voting on Tuesday. Chicago election officials reported some problems with the new law allowing 17-year-olds to vote in the primary if they will turn 18 by the general election in November. Some electronic polling books were not sending the correct signal to allow that.

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In addition, two polling places opened late in the 1st and 7th wards; and there are concerns about processing voters who are registering to vote for the first time. To register, voters must provide two forms of identification, including one showing their current address, but they do not need any photo ID.