Voters in Minneapolis will decide on Tuesday whether to replace their police department with a new Department of Public Safety, more than a year after the murder of George Floyd, a Black man, by a white police officer launched a national movement to defund or abolish police.

The Democratic mayor, Jacob Frey, is also in a tough fight for a second term, facing opponents who attacked him in the wake of Floyd’s death.

Frey opposed the policing amendment. Two of his leading challengers in a field of 17, Sheila Nezhad and Kate Knuth, strongly supported the proposal.

Voters will also decide whether to replace an unusual “weak mayor, strong council” system with a more conventional distribution of executive and legislative powers.

While results on the ballot questions were expected on Tuesday night, the mayoral race uses ranked-choice voting. If no candidate reaches 50% in the first round, the winner will be determined after a tally of second- and potentially third-choice votes.

The future of policing in the city where Floyd’s death in May 2020 launched a nationwide reckoning on racial justice overshadowed everything else on the ballot. The debate brought national attention as well as out-of-state money seeking to influence a contest that could shape changes in policing elsewhere.

The proposed amendment to the city charter would remove language that mandates Minneapolis have a police department with a minimum number of officers based on population. It would be replaced by a new Department of Public Safety that would take a “comprehensive public health approach to the delivery of functions” that “could include” police officers “if necessary, to fulfill its responsibilities for public safety”.

Supporters of the change argued that an overhaul is necessary to stop police violence, to re-imagine what public safety can be and to devote more funding to approaches that don’t rely on sending armed officers to deal with people in crisis.

But opponents said the ballot proposal contained no plan for how the department would operate and expressed fear it might make communities affected by gun violence more vulnerable. The details, and who would lead the new agency, would be determined by the mayor and the council.

Two prominent progressives – Ilhan Omar, who represents the Minneapolis area, and state attorney general Keith Ellison – supported the policing amendment. But some leading mainstream liberals, including Governor Tim Walz and Senators Amy Klobuchar and Tina Smith, opposed it, fearing backlash could lead to Democratic losses across the US in 2022.

Opponents included several Black leaders, some top voices in the police accountability movement. Minister JaNae Bates, a spokeswoman for the pro-amendment campaign, told reporters that even if the proposal fails, it has changed the conversation.

“No matter what happens,” Bates said, “the city is going to have to move forward and really wrestle with what we cannot un-know: that the Minneapolis police department has been able to operate with impunity and has done quite a bit of harm and the city has to take some serious steps to rectify that.”