The accused are on trial accused of targeting Gretchen Whitmer in 2020 over Covid rules she imposed early in the pandemic.
Their lawyers argue they were entrapped - or improperly induced into the crimes - by government agents.
The four are facing charges of kidnapping conspiracy.
Two of the men are also facing charges of conspiracy to use a weapon of mass destruction.
According to prosecutors, a group of men - some of whom are alleged militia members - planned to abduct the Democratic governor from her holiday home with the intent of putting her on a "treason trial" and then setting her adrift in a boat on Lake Michigan.
The FBI arrested 14 suspected kidnappers in October 2020, six of whom were charged in a federal court. The other eight face separate state charges.
Two of the men who were charged federally have since taken plea deals, which included agreements to take the stand against their alleged former co-conspirators - Adam Fox, 38, Daniel Harris, 24, Brandon Caserta, 33, and Barry Croft, 46.
On Wednesday, Ty Garbin, 26, who pleaded guilty in January 2021 to conspiring to kidnap Ms Whitmer, told the court the plotters had hoped their actions might be copied around the country and become the "ignition" for a second US civil war.
The goal, he said, was "to cause as much disruption as possible to prevent Joe Biden from getting into office".
According to Garbin, a former airline mechanic now serving six years in prison, several other ideas were discussed before the kidnapping plan, including fire-bombing state police cars or taking lawmakers hostage in the Michigan Capitol building.
He claimed that, in preparation for the attack, they watched the governor's house, created secret online chat rooms, and even built a makeshift building on his property where they could simulate the abduction. He was to be one of the actual kidnappers, he said.
Much of Garbin's testimony was echoed on Thursday by Kaleb Franks, 27, who took the stand after him. Franks pleaded guilty last month.
He intended to be "one of the people on the front line, so to speak, using my gun", Franks testified.
He said the group had discussed attacking Governor Whitmer's security detail using machine guns and grenade launchers.
Asked why he was with the group, Franks said he "no longer wanted to live" because his life had recently gone downhill. "Getting in a shoot out with police, you'd be bound to die," he said.
Both Garbin and Franks testified that the participants were not forced to stick with the group and chose to do so - contradicting the defence's assertion that the accused were entrapped.
Defence lawyers describe the plot as being angry talk and violent bluster rather than a real plan. They are also trying to compel the testimony of a key FBI informant who they allege acted as a "double agent" while working undercover in the group.
The closely watched trial, which began in early March, is expected to last about six weeks. Prosecutors expect to wrap up their arguments by the end of next week.