Sinn Fein have failed to secure a council seat in the area where murder victim Robert McCartney lived.
Robert McCartney, 33, was killed near Belfast city centre
Republican Deborah Devenny lost out to Alliance in the Pottinger ward, but said the McCartney issue had not affected their vote in Short Strand.
But the victim's sister, Catherine, said the family thought the killing and cover-up had an effect at the polls.
"Sinn Fein, I think, would have retained this seat if it wasn't for Robert's murder," she said.
"I think the community in Short Strand have spoken on this and also feel not enough is being done to help the family get justice."
The Alliance Party said Sinn Fein's first preference vote was down by about 30%.
Ms Devenny, who was eliminated from the election, said the UUP and the SDLP voted tactically to keep Sinn Fein out in Pottinger.
Mr McCartney, 33, was stabbed outside a city centre bar in January.
His family, who live in the Short Strand, insist members of the IRA were involved and that witnesses are afraid.
Deborah Devenny said: "The poll altogether in the Short Strand was 1,129 and out of that, Sinn Fein got 826 votes - which is around 75% of the Short Strand vote.
"This proves that the McCartney issue didn't affect the solid republican vote in the Short Strand area, which the media were focussing on."
She said the Sinn Fein leadership was still working "to get the McCartney family justice".
But Alliance councillor Naomi Long said Sinn Fein's figures showed a sharp drop from the last council election.
"The big difference was how Sinn Fein polled in Short Strand," she said.
"The last time they polled 98% of first preference votes in Short Strand, this time our tallies took it to be between 65 and 70%.
"That is a huge drop and it is clear that the Robert McCartney factor played out in that election."
Successful Alliance councillor Maire Hendron also said the "McCartney factor" had an influence on the Sinn Fein vote.
"There were a lot of spoilt ballots overall in the Pottinger count. There were a number that were obviously Short Strand and people who were protesting about the murder of Robert McCartney."
On Tuesday Sinn Fein's North Belfast MLA Gerry Kelly appeared to concede the murder had some effect.
He told BBC NI's election programme: "I am not denying that there clearly is an effect but we are dealing with a single seat in Short Strand."