Retired Appellate Judge Eileen O’Neill Burke’s tight lead in the Democratic primary for Cook County state’s attorney shrank ever-so-slightly Thursday evening as the last-remaining votes on Election Day from city precincts were tabulated along with a batch of mail-in ballots from the suburbs.

Unofficial results from the Chicago Board of Elections and Cook County clerk showed O’Neill Burke with a 50.8% to 49.2% lead over former prosecutor and government official Clayton Harris III. O’Neill Burke’s total vote count decreased to just 8,152, down from the roughly 8,800 vote lead she held a day earlier.

The county clerk, which oversees suburban Cook elections, logged about 5,900 Democratic votes from mail-in ballots returned on Tuesday and Wednesday. Around the same time, Chicago election officials tabulated the final 11 precincts that hadn’t been reported.

While those results moved the needle somewhat, both campaigns have their eyes set on results expected to be counted Friday evening by Chicago election officials as they begin tallying roughly 26,000 mail-in ballots delivered to the city election offices on Tuesday and Wednesday.

Chicago election judges will have a second, and likely a third, set of eyes on their work. Poll watchers from both campaigns are expected to be on hand to ensure signatures on ballots match the signatures in board records, as well as checking that mailed ballots are postmarked no later than Election Day and ballots being scanned.

In a Thursday campaign email, Harris urged supporters to volunteer for a shift or two through Monday to keep watch on the count.

“Right now, the most important thing you can do to secure our victory is sign up to volunteer at the Board of Elections to monitor the vote counting,” the email read. “This is crucial. We need you now!”

O’Neill Burke has led in totals since Election Day, thanks in large part to an edge in the suburbs. But that advantage has slowly shrunk as more votes, especially those in the city where Harris has lead, have been posted.

“We’re still waiting for votes to be counted,” O’Neill Burke said in a post on the social media platform X, formerly Twitter, on Thursday, “but rest assured that our team is monitoring the process closely, and we are optimistic.”

Roughly 104,000 Democratic mail-in ballots had not been returned by city and suburban voters as of Thursday night. However, election officials and campaigns warned not all of those ballots would be returned, nor would they all contain votes for state’s attorney. Ballots that were mailed and postmarked by March 19 will be counted by city and county officials until April 2.

About 75% of those unreturned ballots were requested by city voters, giving the Harris campaign and his supporters hope they could make up the difference.

City election officials on Election Day said a total of 20 precincts were unable to to report their results from in-person voting that day. With the 11 counted Thursday and nine precincts counted on Wednesday night, those 3,800 new ballots overwhelmingly broke in favor of Harris.

It’s unclear to election officials whether low voter turnout this year means a similarly low number of mailed-in ballots will be returned.

“We may see and we’re not sure that there may be a drop off of those returned because of the same low voter turnout,” Edmund Michalowski, the Cook County clerk’s election deputy, said Thursday. “By next week, we’ll have a much clearer idea just as the post office moves mail through their process” how many ballots will be returned. The clerk’s office will update its numbers again publicly at the end of the day Monday, he said.

Michalowski declined to say how historic mail-in ballot returns might reflect on this year’s tally.

“My name is not Nostradamus,” he quipped.

The scanning and counting of mail-in ballots by Chicago election judges will begin Friday morning, but the results won’t be made public until later that evening, Chicago Board of Elections spokesman Max Bever has said. The board delayed the count by a day after both the Harris and O’Neill Burke campaigns requested that their poll watchers be able to review the processing and counting of mailed ballots.

Chicago’s vote-by-mail scanning and sorting machine, Agilis, scans voter signatures to match against the Chicago Board’s registration records to approve or reject ballots. Scans are captured as PDFs that are reviewed by election judges. Poll watchers can also compare those signatures to voter registration files. Agilis also sorts mail-in ballots by ward based on the address listed on the ballot return envelope.

If a mail-in ballot is properly postmarked but the voter signature or information on the return envelope either doesn’t match or is incomplete, Bever said, “it is initially rejected and will not move onto processing and counting. That voter is sent an email and a paper letter alerting them to the reason their ballot was rejected and how they can cure their ballot status by providing additional identification to the board to process and count that ballot.”

Suburban Cook mail ballots run through a similar process — a sorting machine captures both the signature and the address on the ballot’s envelope. A bipartisan panel of election judges review each to make sure the signature in the voter file matches the signature on the envelope. Postmarks are manually checked. Ballots are removed from the envelope, scanned and anonymously tallied. Any issues with timely ballots also are flagged by suburban officials and voters get an email and a letter giving them an opportunity to rectify any issues.

Michalowski estimated 150 suburban election judges were working at the county’s operation center Thursday.

“There’s so many people that have constant eyes on this,” he said.