Northern Ireland's constitutional future would be thrown up in the air if Sinn Fein was to emerge from the Assembly election as the largest party, Democratic Unionist leader Arlene Foster has warned.
Mrs Foster said such a result would see the UK Government come under renewed republican pressure to hold a referendum on a united Ireland.
The DUP leader said she made "no apologies" for adopting a campaign line that has been branded as another version of "project fear" by political rivals.
"I am not going to apologise for the fact there's a huge threat to Northern Ireland," she said.
"People have talked about scare tactics and talked about fear, the reality (of a Sinn Fein victory) would be much worse for Northern Ireland than just talking about it.
"People should be concerned, they should be worried."
The region faces a snap poll on Thursday after Sinn Fein pulled the plug on the devolved institutions in protest at Mrs Foster's handling of a botched green energy scheme that had left Stormont facing a potential overspend of almost £500 million
Mrs Foster claimed the renewable heat incentive (RHI) affair was not the republican party's real motivation.
"They wanted to take me out, they wanted to weaken unionism, I understand all that but this election is much more important than one individual," she said.
The power to call a border poll rests with Northern Ireland Secretary James Brokenshire, legislation dictates he should take the step if there is evidence of a clear shift in public opinion in favour of Irish reunification.
Mrs Foster said Sinn Fein displacing the DUP in the First Minister's office would be seized upon by republicans as such evidence.
Critics have accused the DUP leader of turning an election about alleged financial mismanagement into a traditional green/orange battle in a bid to deflect the public attention from RHI.
Rivals have also claimed her repeated reference to Sinn Fein president Gerry Adams, who is not standing in the election, is an example of using a "bogeyman" to galvanise the unionist vote.
Mrs Foster defended her approach, dismissing those who highlight the fact Stormont's First Minister has exactly the same power as the Deputy First Minister.
"We must be the only country in the world where it doesn't matter who wins the election," she said.
"That's just wrong, of course it matters who wins the election.
"We are not just talking about the system of government, you are also talking about what it says to the world, what it says to our government about where we are in terms of a border poll
"If they have the larger number of seats in the Assembly they will push for a border poll.
"That will be very divisive, very destabilising for Northern Ireland at any time, but particularly at a time when we are dealing with our exit from the European Union."
Of the DUP's desire to retain its position as the biggest party, she added: "It's not just about the First Minister's office, it's about how we drive the agenda forward for Northern Ireland, it's a recognition that the majority of people in Northern Ireland want to stay in the United Kingdom.
"If we had a situation where Sinn Fein were the largest party all of that would be thrown up in the air and we would get to a situation where they would be pressing the Government for a border poll."
The DUP leader rejected any suggestion her stance was detrimental to the wider task of forging reconciliation between nationalist and unionists in Northern Ireland.
At one point in the campaign Mrs Foster referred to Sinn Fein representatives as "crocodiles".
"Look at my record," she said.
"Nationalism has absolutely nothing to fear in relation to the way in which I do my business.
"I work with everybody, I will try to help everybody if they need help."
