Matthew DePerno, a key orchestrator of efforts to help former President Donald J. Trump try to overturn the 2020 election in Michigan and an unsuccessful candidate for state attorney general last year, was arraigned on four criminal charges on Tuesday, according to documents released by D.J. Hilson, the special prosecutor handling the investigation.

The charges against Mr. DePerno, which include undue possession of a voting machine and a conspiracy to gain unauthorized access to a computer or computer system, come after a nearly yearlong investigation in one of the battleground states that cemented the election of Joseph R. Biden Jr. as president.

Former State Representative Daire Rendon was also charged with two crimes, including a conspiracy to illegally obtain a voting machine and false pretenses.

Both Mr. DePerno and Ms. Rendon were arraigned remotely on Tuesday before Chief Judge Jeffery Matis, according to Richard Lynch, the court administrator for Oakland County’s Sixth Circuit, and remained free on bond.

The charges were first reported by The Detroit News.

The criminal inquiry in Michigan has largely been overshadowed by developments in Georgia, where a grand jury is weighing charges against Mr. Trump for trying to subvert the election, but both are part of the ongoing reckoning over the conspiracy theories about election machines promoted by Mr. Trump and his allies.

The efforts to legitimize the falsehoods and conspiracy theories promoted widely by Mr. Trump and his allies continued long after the Jan. 6, 2021, attack on the Capitol and after Mr. Biden took office. In Arizona, such efforts included the discredited election audit of Maricopa County led by Republicans in the state legislature.

In a statement, Mr. Hilson said, “Although our office made no recommendations to the grand jury as to whether an indictment should be issued or not, we support the grand jury’s decision and we will prosecute each of the cases as they have directed in the sole interests of justice.”

The charges stemmed from a bizarre plot hatched by a group of conservative activists in early 2021 to pick apart voting machines in at least three Michigan counties, in some cases taking them to hotels and Airbnb rentals as they hunted for evidence of election fraud.

In the weeks after the 2020 election, he drew widespread attention and the admiration of Mr. Trump when he filed a lawsuit challenging the vote tallies in Antrim County, a rural area in Northern Michigan where a minor clerical error fueled conspiracy theories.

He falsely claimed that voting machines there had been rigged, a premise that was rejected as “idiotic” by William P. Barr, an attorney general under Mr. Trump, and “demonstrably false” by Republicans in the Michigan Senate.

Last August, Michigan’s attorney general, Dana Nessel, a Democrat who went on to defeat Mr. DePerno in the November election, asked for a special prosecutor to be appointed to consider criminal charges against him and eight other election deniers in connection with what Ms. Nessel characterized as the illegal tampering with voting machines used in the 2020 election.

Ms. Nessel referred to Mr. DePerno as “one of the prime instigators of the conspiracy,” but said it would not be appropriate for her to conduct an investigation into Mr. DePerno, who was her political opponent at the time.

Mr. Hilson, the prosecutor in Muskegon County appointed as special prosecutor, had initially delayed bringing charges, asking a state judge to determine whether it was against state law to take possession of a voting machine without the secretary of state’s permission or a court order. A judge determined last month that doing so was against the law, clearing the way for charges.

Democrats swept the governor’s race and other statewide contests last fall, in addition to flipping the full Legislature for the first time in decades. Mr. DePerno, who was endorsed by Mr. Trump, lost the attorney general’s race by eight percentage points.

This year, Mr. DePerno had been a front-runner to lead the Michigan Republican Party after its disappointing showing in last year’s midterm election, but he finished second to another election-denier: Kristina Karamo.

In his campaign to lead the G.O.P. in Michigan, Mr. DePerno had vowed to pack the party’s leadership ranks with Trump loyalists, close primaries to just Republicans and ratchet up the distribution of absentee ballot applications to party members — despite what he said was lingering opposition to voting by mail within the party’s ranks.

His candidacy was supported by Mike Lindell, the MyPillow chief executive who has spread conspiracy theories about election fraud and appeared at a fund-raising reception for Mr. DePerno in Lansing on the night before the chairmanship vote.

Mr. DePerno lost to Ms. Karamo after three rounds of balloting at the state party convention, a process that was slowed for several hours by the use of paper ballots and hand counting.

Danny Hakim contributed reporting.