Angela Roberts, a Taranaki-based MP, said she was chatting to constituents after a campaign debate in Inglewood when she was taken to task by "a tall man" over education policy, before being grabbed by the shoulders, shaken and slapped.
"It's important to take a stand and call out this aggression," she said in a Facebook post.
"It feels like, incrementally, there is a growing acceptance of aggression in politics and our democratic processes. This must change.
"We need to ensure that New Zealand is a safe place for democracy to thrive, a safe place for those who are curious about the implications of their voting decisions and a safe place for political candidates."
Ms Roberts thanked her opposition candidate, National MP Barbara Kuriger, for supporting her during the alleged assault.
It is not the first report of harassment during a charged election campaign.
Speaking alongside Prime Minister Chris Hipkins in Kawakawa on Thursday, Northland MP Willow-Jean Prime said she had felt unsafe and heckled when using Maori words during a debate earlier in the month.
"Whenever I said a te reo Maori word like 'puku' for full tummies... I was shouted at. When I said 'Aotearoa', the crowd responded, 'It's New Zealand,'" Ms Prime said.
"That is racism. I have never experienced that level of vitriol ... it's becoming a bit of a theme. It feels like there is dog whistling going on."
Mr Hipkins said he had felt a scaling up of tension in the electorate.
"There certainly does appear to be more risk in this election than we've seen in recent elections," he said.
"It is a reminder that election campaigns should be conducted with respect and with dignity."
The place of Maori in NZ has been uneasily examined during this campaign.
Parties from the right - including poll leaders National, libertarians ACT and populists NZ First - have vowed to wind back elements of the Labour government's "co-governance" program, which gives Maori enhanced decision-making in government.
That includes Labour's water reforms - which offer Maori a 50-50 split on governance boards - and the new Maori Health Authority, which Labour has set up to end health disparities.
National, ACT and NZ First decry the agency as a separatist system.
In a televised debate this week, Mr Hipkins also challenged alternate prime minister Chris Luxon to disavow racism from a lowly-ranked NZ First candidate by refusing to go into a coalition with the party.
Mr Hipkins then doubled down on the attack, saying National was pandering to anti-Maori voters by disestablishing the Maori Health Authority.
Mr Luxon countered by calling Mr Hipkins - whose Labour party is well behind in the polls - desperate.
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