After a long night of eye-crossing work, Denver election signature verifiers at the Clerk and Recorders Office were back at their desks on Wednesday, dressed in their most comfortable clothing, eyes tired.

The white board along a wall in Denver’s ballot verification room announced a final schedule update: “We made it!”

By Thursday afternoon, bipartisan teams of two finished comparing voters’ signatures on incoming ballots. They’ve been at it since Oct. 14.

These signature experts verify an average of 300 signatures per hour, comparing a voter’s most recent signature with the handwriting on their 2024 ballot. When the handwriting doesn’t match, the ballots are challenged.

Thousands of ballots identified by red “Challenged Ballot” signs waiting in U.S. Postal service tubs.

In a CSI moment, Denver’s eagle-eyed group caught a batch of 60 ballots with mis-matching signatures that, suspiciously, were traced to a similar mailing address — a senior day care center in southeast Denver.

The home addresses were different. They showed that the dozens of potential fraudulent ballots involved residents who had homes in six counties: Denver, Jefferson, Adams, Arapahoe, Douglas and Boulder.

District attorneys and investigators from those counties are looking into exactly what happened.

“We identified the ballots and stopped the bleeding,” said Denver Clerk and Recorder Paul Lopez, still standing on three hours of sleep. On Wednesday, he wore a black ball cap with the words “VOTE” across the front in white letters.

Colorado voters from across the political spectrum are happy with the state’s voting system and give local officials high marks for the way they administer elections, according to statewide exit polling released last week by a bipartisan public opinion research consortium.

The pollsters said Colorado voters are “overwhelmingly” satisfied with the state’s mail-ballot election system, which allows voters to return completed ballots by mail or at drop boxes, or to vote in person at voter service centers. Overall, 87% of voters said they approve of the system, with 72% of Republicans and 99% of Democrats giving a thumbs up. Additionally, 70% of Trump voters said they were satisfied with the state’s system, as did 99% of Harris voters.

Asked to grade local election officials on how well their elections are run, 72% of voters assigned an A or B, while just 12% gave officials a D or F.

So, how do elections workers keep people from cheating by casting votes on ballots that are not their own, which they have to sign?

“Training,” said Elections Director Todd Davidson.

Many of the signature verifiers are veterans. On the wall is a poster with examples of what to look for, referencing familiar autographs — Richard Nixon, Millard Fillmore and James A. Garfield. The spacing between the “s” in James and the capitol “A” are circled in red.

Others go through four hours of online and in-person workshops to identify the position of signatures, how rapidly people signed their names, spelling and punctuation.

This year, more than 350,000 ballots came through the Denver Clerk and Recorder’s office. They are driven to a fortified door from 45 ballot boxes, mailed or filled out in-person.

Lopez oversaw several hurdles this election season. There was the case of the online disclosure of hundreds of election equipment passwords on the Secretary of State’s website, and his battle with the Colorado Democratic Party because of its choice of having the election night watch party near a polling place.

Also, the power shut down during voting at Denver’s Christ Church United Methodist Fellowship Hall after a squirrel had a run-in with a transformer.

Officials have maintained that Colorado’s system is known as one of the safest in the country, but Mesa County discovered at least 12 mailed ballots were stolen and then sent in with fraudulent votes, three of which slipped past county election officials and were counted in the general election

To alleviate the risk of stolen ballots, in Denver, all 45 ballot boxes are monitored 24/7 with human eyes behind surveillance cameras. The slot in which a voter drops a ballot is so thin, no hand could get inside to snag an envelope. They’re bolted to the ground and fire resistant.

This year, the worst image caught by ballot receptacle cameras was of a person who pasted a campaign sticker on the box. Another was tagged with graffiti, according to Voter Service Manager Jake Harvey.

In the case of the 60 possible fraudulent signatures, investigators are conducting interviews to track exactly what happened and criminal charges could be pending.

Every ballot must be certified by the Colorado Secretary of State by Nov. 22.