Christopher Thomas spent 36 years as director of Michigan’s elections, overseeing the laborious but uncontentious running of presidential vote counts.

Then came 2020. Within hours of the polls closing in the presidential race, roving bands of Donald Trump’s supporters were moving from table to table at one of Detroit’s principal counting centres, flinging around accusations of vote rigging as they challenged and intimidated poll workers in the key swing state.

“These folks rolled in as a result of social media telling them to get down there because everything was being stolen. So they all came in, pretty revved up. I’m not expecting that,” said Thomas.

Several hundred descended on the convention centre where about 170,000 postal ballots were collated in the overwhelmingly Democratic city. Some yelled “stop the count”. Others taunted the vote counters. Groups of Trump supporters, locked out when the situation became too unruly, pounded on windows and doors.

In the end, the count continued and Joe Biden overturned Trump’s slim victory in Michigan four years earlier, helping to push the then president out of the White House.

But as Michigan heads into crucial midterm elections, and with the next presidential race swinging into view, both sides have learned lessons.

The state’s Republicans have launched a coordinated effort to pack the process of overseeing elections with partisan poll monitors, while recruiting lawyers and sympathetic law enforcement officials ready to wade in to disputes, in what appears to be a strategy to create enough confusion and disagreement that unfavorable results are thrown into doubt. That potentially opens the way for the courts or, in the electoral college process for the presidential election, the Republican-controlled state legislature to intervene.

All of this fits with the “precinct strategy” pushed by Steve Bannon, Trump’s former strategist who has been sentenced to four months in prison for contempt of Congress, to shoehorn grassroots Trump supporters into low-level positions across the country, such as election administration and on school boards, in order to take control “village by village … precinct by precinct”.

Thomas, who retired as elections director in 2017 but continues to consult for the Detroit city clerk, is concerned.

“I’m watching these efforts to enlist partisan poll workers with some scepticism,” he said.

Michigan’s 83 elected county clerks oversee elections in their jurisdictions with some authority delegated to city and township election officials. They include Barb Byrum, a Democrat who has spent the past 10 years as Ingham county clerk after five years as a state legislator.

“We really started seeing the attack on our elections over six years ago but it has really ramped up,” she said.

“There’s a concerted effort by the Republicans to encourage individuals to be hired by local clerks to work the election but then also serve as spies basically for the Republican party. They have been encouraged to sneak cellphones into the absentee county boards and call select Republican attorneys during election day.”

Byrum, who was once barred from speaking during an anti-abortion debate in the Michigan legislature for using the word “vasectomy”, said illicit cellphones, which are barred from the count, put the “secrecy of the ballot at risk”.

Political parties also get to appoint challengers who can question whether a person is qualified to vote. Byrum said that opens another avenue for disruption if the challengers make bad faith interventions that create long lines in strongly Democratic areas and discourage people from voting.

In June, Politico revealed video recordings of the Republican National Committee election integrity director for Michigan, Matthew Seifried, telling party activists that there was going to be “an army” of poll challengers at work in Detroit and beyond who would be kept in touch with legal teams ready to move in at any claim of irregularity.

“We’re going to have more lawyers than we’ve ever recruited, because let’s be honest, that’s where it’s going to be fought, right?” he said.

Politico also obtained recordings of the legal counsel to the Trump-aligned Amistad Project, Tim Griffin, discussing plans to mobilise sympathetic district attorneys to launch investigations into allegations of voter and counting irregularities.

“Remember, guys, we’re trying to build out a nationwide district attorney network. Your local district attorney, as we always say, is more powerful than your congressman,” Griffin told activists. “They’re the ones that can seat a grand jury. They’re the ones that can start an investigation, issue subpoenas, make sure that records are retained, etc.”

Last year, Michigan’s Republican party chose a Trump supporter, who said he would not have certified Biden’s election victory, to serve on the body that certifies elections in Detroit and its surrounding county. Robert Boyd said he regards the 2020 presidential election results as “inaccurate” because of events at the disrupted Detroit count.

Boyd, who has blamed the 6 January 2021 storming of the Capitol on Black Lives Matter and antifa “agitators”, is one of two Republicans on the Wayne county board of canvassers alongside two Democrats. If they deadlock on whether to certify future elections, that could open the way for legal challenges to the result and the intervention of the state legislature. The Republican legislature has the authority to overturn the popular vote and appoint its own choice of delegates to the electoral college for the president, although it would be an unprecedented move that it declined to take in 2020.

Still, Byrum said Republican attitudes had hardened and she saw a concerted effort to create disruption and disputes to open the way for legal and political intervention to challenge election results they don’t like.

“I think this is a direct attack on our democracy because this is a concerted effort to undermine the integrity of our elections, and ultimately, attack our democracy,” she said.

In response to the disruption, the state’s elections board has tightened regulations to prevent groups of poll monitors from roaming around from one counting table to another to prevent intimidation. Thomas said there are already regulations in place to prevent frivolous or repeated challenges against voters. They have rarely been used in the past.

“We have certainly reorganised how we control the environment there compared to 2020 having never seen anything like that in the years before,” he said.

Thomas took some comfort from the relatively smooth passing of August’s primary elections.

“There’s one group, called Election Integrity Group, they can be a bit on the obnoxious side. But we can all tolerate a little bit of obnoxiousness. They didn’t interfere with the process,” he said.

“Of course, the Republicans didn’t really have much at stake in the city of Detroit in the August primary. So we’ll see when stakes go up as we get to the general.”

Justin Roebuck, the Republican county clerk and chief elections officer for Ottawa county, said the atmosphere was fraught, with his office still dealing with a flood of freedom of information requests looking for evidence of fraud in the presidential election.

“Over the past couple of years, we’ve seen the level of disinformation that came out of the 2020 election cycle has really amplified and solidified in some ways. That misinformation has really taken root in a certain percentage of our population,” he said.

“Folks are still asking to see all sorts of things like the voted ballots from the 2020 election. They’re asking to see the digital imaging of our software that was used to programme the 2020 election. They’re coming from all over the place, and not just voters here in my jurisdiction or in Michigan. They’re coming from around the country.”

Roebuck, like clerks in other counties, has sought to reassure voters with greater transparency about how the counting process works and in the training of poll workers. He said that many of them are persuaded of the legitimacy of the vote once they see the system at work. But, like Thomas, he said there was a small hardcore intent on challenging any outcome they do not like.

“There’s probably about a 10% portion of the population that has truly bought into the notion that our elections were stolen, and I’m not sure how successful I will be in convincing those folks because I have had a lot of those conversations where it’s just very difficult to get through to people with the facts,” he said.

The democratic process is also under pressure from some local officials spreading false accusations that the elections they are overseeing may be rigged.

Last year, Michigan’s bureau of elections stripped the Republican clerk of Adams township, Stephanie Scott, of her authority to run the municipal election after she refused to submit a vote tabulating machine for routine testing.

“The county clerk’s office and now secretary of state are demanding I drop off my machine for unfettered access, and God only knows doing what to it,” she told the Bridge Michigan news site.

“When you have the fox guarding the henhouse, somebody’s got to stand up and guard those hens.”

The township supervisor, Mark Nichols, backed Scott, saying that voting machines “have been a tool to steal our elections” and 2020 was “the year of the lie” .

The Michigan bureau of elections director, Jonathan Brater, wrote to Scott accusing her of making “numerous false statements” when she questioned the integrity of the vote at a township public meeting.

“By communicating false or misleading information about elections in Michigan, you risk not only undermining confidence in democracy in your community, but also amplifying threats and intimidation of your fellow election officials across our state which, fueled by misinformation, continue unabated,” Brater told Scott.

Brater also had to warn local election officials to ignore a cease and desist letter from the Republican candidate for Michigan attorney general next month, Matthew DePerno, demanding they cancel planned voting machine maintenance because it could “destroy or alter” voting records he alleges are fraudulent. DePerno beat two Republican rivals after Trump backed him in the primary election.

One Michigan county clerk hired a Trump supporter to recruit poll workers who was filmed urging people to storm the Capitol in Washington on 6 January 2021 and joined white nationalist Proud Boys rallies at the state legislature.

All of this leaves Roebuck despairing of his own party: “Our voters deserve honesty. Sometimes it can be a political advantage for candidates to go down a different path to use talking points about election integrity or election misinformation, but I don’t think it’s an advantage to our society in the long term,” he said.