A month ahead of the the Iowa caucuses, presidential contenders can officially file to run in neighboring Illinois.
Five Republicans got their petitions in early Monday, with at least 3,000 signatures each.
The Illinois Republican Party's attorney John Fogarty says the popular vote for president is known here as the "beauty contest."
That's because who Illinois GOP primary voters pick as delegates -- who are listed on the ballot as supporters of a particular candidate -- is where the race is really won.
Often, campaigns look for big-names to run as delegates. That can be difficult.
"What's going to be interesting to see is which of these campaigns files with full delegate slates, and how may many they file with, etc.," Fogarty said. "What will be interesting as well is to see whether or not any campaign objects to any other. It's sort of been the tradition that all the major players respect each others' delegate slates, and don't use our objection process to try to clear the ballot for any Presidential campaign. My hope is that that will continue, and my sense is that it will."
Fogarty, who as a private elections attorney is with Ohio Gov. John Kasich's campaign, says Republicans did change their rules some this year so that Illinois' so-called "at large" delegates will be binded to the winner of the popular vote.
Democrats need delegates too, but the party's hybrid -- and even more complicated -- system also factors in the true top-of-the-ticket results.
So far, Hillary Clinton is the only major Democrat to have filed. Her delegates include a host of current and former public officials, and the wife of House Speaker Michael Madigan. A press release indicates supporters for Vermont Sen. Bernie Sanders, who's seeking the Democratic nomination, will submit his petitions Wednesday.
The Republicans who turned in petitions Monday morning when the state elections board opened its doors are: Jeb Bush, Chris Christie, Ted Cruz, Marco Rubio, and Donald Trump. Those candidates will be in a lottery later this month to decide who gets the top of the ballot spot.
One oddity: an Orland Park Man has filed as a delegate for both Christie and Trump, something which Fogarty says Republican rules do not allow, as delegate hopefuls must sign sworn statements, effectively pledging their loyalty. Fogarty couldn't say how the situation would pan out, for the man or for the Christie and Trump campaigns.
Candidates and their slates of delegates must have filed by close of business Wednesday to run in Illinois' March 15 primary race.