ACT's political troubles have stoked debate on a forthcoming electoral referendum and whether voters may be more likely to ditch MMP.
Peter Shirtcliffe from the lobby group Put MMP To The Vote says people wanting minor parties like ACT to have less influence should vote against the Mixed Member Proportional system.
Prime Minister John Key has raised the prospect that ACT's problems could increase the likelihood of people voting MMP out in next year's referendum.
Mr Shirtcliffe believes Mr Key is right and favours the Supplementary Member system, which he says would result in minor parties having a smaller presence in Parliament.
Sandra Grey from the Campaign for MMP says a modified MMP system is what voters with concerns should go for.
Ms Grey says there is some public concern about the influence of smaller parties, but many people do vote for them.
A referendum to be held in conjunction with next year's general election will ask voters if they want to retain MMP.
If a majority opts for change, a second referendum will be held in 2014 to chose between MMP and the most preferred alternative.