Inmates within America’s overflowing prisons are marking the end of a 19-day national prison strike on Sunday with a new push to regain the vote for up to 6 million Americans who have been stripped of their democratic rights.

The strike was formally brought to a close on the anniversary of the 1971 uprising at Attica prison in upstate New York. Though details of the protest have been sketchy since it was launched on 21 August, hunger strikes, boycotts of facilities and refusal to carry out work duties have been reported in many states, from Florida and South Carolina to Washington.

Now that the strike has ended, organisers hope its momentum can be sustained as they attempt to fulfill their demands including the restoration of the vote. Not only does the US have the world’s largest incarcerated population – 2.3 million are behind bars – it also harbors at state level some of the harshest felony disenfranchisement laws in the world.

According to the Brennan Center for Justice, 34 states bar citizens from voting based on past convictions. Kentucky, Florida and Iowa cast anyone with a felony out of the democratic process for life.

Prisoners are beginning to coalesce around the push to regain the vote as a means of forwarding the cause of prison reform. The effort is led by Jailhouse Lawyers Speak, a loose network of imprisoned women and men who were at the forefront of the national prison strike.

When the strike was launched, its organisers put out 10 demands. The 10th was that “voting rights of all confined citizens … must be counted. Representation is demanded. All voices count.”

Eddie, a prisoner who has served 13 years of an 18-year sentence for armed robbery in South Carolina, said that when he is released in 2023 he will be effectively ostracized.

“I will pay taxes but I won’t be able to vote,” he said.

Speaking on a clandestine phone from his prison cell, Eddie, who asked not to give his proper name to avoid reprisals from authorities, said disenfranchisement condemned prisoners to the status of second-class citizenship.

“It lets me know that I’m not truly a citizen,” he said. “I will have no say in the political process or the direction of the nation.”

Eddie is one of the organisers of Jailhouse Lawyers Speak involved in coordinating strike action. He said that in his prison most activity had focused on boycotting facilities that generate cash for the prison service, such as commissaries and vending machines in the visitors’ room.

There had also been widespread refusal to work in his and other South Carolina penal institutions. The striking inmates see the obligation of performing prison work for minimal or no pay as a 21st century form of slavery.

In response, Eddie said, South Carolina maximum security prisons had been held in a state of lockdown throughout the strike.

They have suspended all recreation so that we are in our cells literally 24/7 Eddie, inmate and Jailhouse Lawyers Speak organiser

“They have suspended all recreation so that we are in our cells literally 24/7,” he said. “They turn back our mail, threaten anyone found to be associated with the strike with solitary, and they’ve painted windows in our cells black so we have no idea whether it’s night or day.”

Such intimidation failed, he said, to dampen spirits or dissuade inmates as they plan future actions. Of those, one of the key efforts he said will now be around voting rights.

Other retaliatory moves have been reported against prominent prisoner activists and strike organisers. Kevin Rashid Johnson, who wrote an opinion piece for the Guardian at the beginning of the prison strike, has been summoned to appear on Monday in front of the authorities in Sussex state prison in Waverly, Virginia, where he is currently being held in solitary confinement.

Johnson has been told that he faces transfer to a different penitentiary, following a pattern in which he has been moved around the country from prison to prison, from Virginia to Oregan, Texas, Florida and back to Virginia. “This is a form of retaliation,” his attorney, Dustin McDaniel, said. “The authorities object to the way he exposes injustices inside the system and that he does political education work with other prisoners, and so they move him around to try to neutralise him.”

While strike leaders are primed for further retaliatory measures, they are also developing the campaign to restore voting rights. Janos Marton of the American Civil Liberties Union Campaign for Smart Justice, which aims to cut the US jail and prison population in half, said a renewed focus on felony disenfranchisement was one of the main achievements likely to flow from the past 19 days of actions.

“Organising across states for the strike has mobilized prisoners as a unified voice to an extent we have never seen before,” he said.

Marton added: “The most tangible impact of that amplified voice after the strike ends is a specific effort over voting rights.”

The issue of the removal of the vote from millions of prisoners is likely to be a hot button issue during the midterm elections in November. In Florida, voters will be asked as a constitutional amendment whether they want voting rights to be restored to people with felony convictions who have fully served their sentences and completed parole or probation.

Florida is traditionally one of the most finely balanced and important swing states, with the potential to decide presidential elections. Donald Trump won there in 2016 with a majority over Hillary Clinton of just 113,000 votes. If voting rights were restored, some 1.5 million Floridians would be brought back on the voting rolls.

In other states, Republican officials have been aggressively applying disenfranchisement laws to the extent of sending former inmates back to prison simply for trying to vote.

In Texas, Crystal Mason faces returning to federal penitentiary on 13 September for 10 months after she cast a provisional ballot in the 2016 presidential election. She was not aware at the time that as a former felon, she was prohibited from voting.