Donald Trump will return to Michigan on Saturday for his first visit since November 2020 when he spent the final hours of his presidential election campaign desperately trying to hold on to the state and fend off nationwide defeat to his Democratic rival Joe Biden.

This time his visit will be motivated by an attempt to forge a path to victory in the 2024 presidential election, in which he has hinted he may run again. If that is his intention, he is going about it in a very irregular fashion.

His guest of honor at the rally he is staging in Washington Township will be bear no resemblance to the local politicians whom former US presidents normally champion. Kristina Karamo is a part-time community college professor who has never held elected office and who up until 18 months ago was relatively little known outside conservative and religious circles in the Detroit suburb in which she lives.

Karamo, 36, describes herself as a defender of the Christian faith and espouses some arresting beliefs. She opposes teaching evolution and has called public schools “government indoctrination camps”; she argues that many Americans live in poverty because “they just make dumb decisions”; and she contends that the instigators of the January 6 insurrection at the US Capitol were “totally antifa posing as Trump supporters”.

There are two clues as to why Trump is willing to make the 1,200-mile schlepp from his home in Mar-a-Lago, Florida, to chilly Michigan on Karamo’s behalf. The first is the position for which she is standing in November’s midterm elections – secretary of state.

The post-holder acts as chief elections officer in Michigan, and in that capacity will have considerable sway over how the presidential election is conducted in 2024. What happens in the state could then in turn have enormous national implications: in both 2016 and 2020 Michigan was pivotal in securing the White House for Trump and Biden respectively.

The second clue to Trump’s thinking is the language he used when he endorsed her last September. “She is strong on crime,” he said, “including the massive crime of election fraud”.

What initially drew Karamo to Trump’s attention was the prominent role she played in Michigan in promoting his “big lie”, the false conspiracy theory that the 2020 election was stolen from him. From almost total obscurity, Karamo was thrown into the limelight when she began to cry foul about what she claimed was illegal vote counting in the overwhelmingly African American city of Detroit.

It all began with a basic misunderstanding.

As America held its breath in the days after the election, when it remained uncertain whether Biden or Trump would win, Karamo relocated herself to the TCF Center in downtown Detroit where poll workers were counting 174,000 absentee ballots. Karamo was one of scores of Trump supporters who – without any formal training in election procedures or laws – designated themselves as “poll challengers” watching over the politically-charged count.

The convention space was packed to overflowing, with about 900 poll workers counting ballots, as another 400 or so media and political observers looked on. Over the next 24 hours, TCF began to resemble, in the description of the Detroit Free Press, a high-stakes sports match “complete with yelling, taunting, cheering, fists pounding on glass and unruly challengers being hauled off by cops”.

Amid the melee, Karamo claimed that she personally witnessed fraudulent activity in which ballots were switched illegally from Trump to Biden. A week after the election, by which time Biden had been declared winner, she filled out an “incident report” in her neat closely-spaced handwriting.

The three-page document looks like an official police report, though the small print at the bottom says: “Paid for by Donald J Trump for President, Inc.” In it, Karamo gives her account of what she claims to have witnessed.

She was standing at an “adjudication table” where ballots that are incorrectly filled in are scrutinized. She spotted a ballot on the screen in which a voter appeared to have cast their ballot along straight-party lines but for both main parties.

That was clearly an error as you can’t vote for more than one presidential candidate at a time.

Karamo says in the “incident report” that she watched as a poll worker unilaterally decided to award the ballot to Biden, no questions asked. When she complained and called for a supervisor, she claims she was told not to talk to the election staff.

The supervisor, she wrote, instructed the poll worker “to ‘push it through’, when the ballot legally should have been rejected. I said I’m challenging the ballot… but he continued to tell the worker to push it through.”

That sounds like a blatant abuse of election integrity, taking an effectively spoiled ballot and counting it for Biden. Karamo was incensed, and on the back of that eruption of anger began her meteoric rise as an advocate for Trump’s big lie that the election was rigged.

The problem was that Karamo’s interpretation of what happened to the wrongly-completed ballot was based on a simple misreading of election procedure. Chris Thomas, Michigan’s former director of elections who oversaw the state’s vote counts for 36 years under both Republican and Democratic administrations, told the Guardian why.

He explained that when Karamo heard “push it through” she assumed that meant “give the vote to Biden”. But that was a misunderstanding.

In fact, the edict “push it through” when issued at the adjudication table is in effect an order to discard “overvotes” – ballots like the one Karamo witnessed where more than the maximum number of candidates are selected.

“‘Push it through’ means you are done with it, and the vote is tabulated as a non-count,” Thomas said.

In other words, the call to fraudulently count the ballot for Biden which Karamo thought she had heard was in fact an instruction to place the vote in the electronic equivalent of a dustbin where it would be stored but discounted.

What did Thomas make of the fact that Karamo made a hue and cry about fraud based on a mistaken interpretation of electoral practices? “This is the problem when people make all these comments when they don’t understand the system,” he said. “They see what they want to see.”

Thomas was present inside the TCF Center for the duration of the two-day count, working as a senior consultant and handling disputes. With his almost four decades of non-partisan experience of orchestrating elections, how would he rate the way the ballots were handled inside the space?

“The count was totally above board,” he said. “It was accurate and it was fair. The count was good.”

That one mistaken claim of fraud propelled Karamo into the dizzy heights of the Trump firmament. Sean Hannity billed her as a “whistleblower” on his primetime Fox News show, she was invited by Republicans to testify before a legislative committee, she participated in a four-state lawsuit seeking to overturn the presidential election result that went all the way up to the US supreme court (which promptly rejected it).

Emboldened, her baseless critique of rampant election fraud became more forthright. “I was a poll challenger at TCF Center in Detroit,” she told the podcast Coffee and a Mike. “I saw illegal activity and I realized if we don’t cure our election system we no longer have a republic, we have a fake country, an illusion of a country, so I have to do something.”

That “something” was to stand for Michigan secretary of state – a position that would potentially allow her to take her discredited views on voter fraud and use them to Trump’s advantage in 2024. So far, she is doing very well in the race, with a credible shot at prevailing.

With Trump’s enthusiastic backing, she has amassed a campaign war-chest of more than $228,000, more than any other Republican vying for the secretary of state nomination. As an indication of how much heat the race is generating, Karamo has attracted more than 2,000 individual donors – more than all candidates combined in the last secretary of state contest in 2018.

Michigan’s incumbent secretary of state, Jocelyn Benson, is running for re-election as the Democratic candidate. She told the Guardian that the steam that has built up around the race this year is an indication of its high stakes.

“This secretary of state race is the top targeted race in the country, and I am the top targeted incumbent secretary of state seeking re-election this year. Trump’s decision to endorse someone running against me, and his rally on Saturday, are a warning that what is unfolding here should be on everyone’s radar – democracy is on the ballot in November,” Benson said.

Benson was in charge of the presidential election count in Michigan in 2020, which Biden won by 154,188 votes. She believes Karamo was present in the TCF Center “simply for the purpose of interfering with the counting process, causing chaos and confusion and spreading misinformation”.

Asked what would happen if the Trump-supporting conspiracy theorist won in November and took her job, Benson replied: “Michigan would have a chief election officer more than willing to find those extra votes if the candidate asked them. It would be akin to putting an arsonist in charge of the fire department, or giving the keys to the vault to a bank robber.”

As the secretary of state contest gains momentum, progressive groups are mobilizing to try and stop Karamo. The left-leaning End Citizens United/Let America Vote has launched a new “democracy defender program”, investing $7m in secretary of state and attorney general races where Trump-endorsed big lie candidates are on the ticket.

“Karamo sought to silence and overturn the will of Michigan voters. Her false and extreme rhetoric is a threat to democracy because it undermines faith in our elections,” said a spokesperson for the group, Tina Olechowski.

The Guardian reached out to Karamo, but she did not respond.

As the race hots up she continues to claim that Trump won the 2020 election and to demand a “forensic audit” of the results – even though “forensic audits” do not exist under Michigan election law. In October she spoke at a QAnon convention in Las Vegas where she joined other pro-Trump big lie candidates running for secretary of state positions around the country.

“She was one of several political candidates appealing to QAnon for political gain in ways that could have a drastic impact on future elections,” said Alex Kaplan, senior researcher at the watchdog Media Matters for America.

Karamo has said that if she wins in November, her role as secretary of state will be “to make sure elections are secure and that the result represents the will of the people, not those corrupting the system”.

That’s not how Benson sees it. Karamo, she said, is one of several Trump-endorsed secretary of state candidates around the country who appear willing “to violate their oath, the law and the principles of our democracy in service of their party and their private agenda”.

And if that happens, Benson said, “then democracy will have been dealt perhaps its greatest blow since the origins of our country”.