SINN Féin deputy leader Mary Lou McDonald has said a "stark set of choices" is facing the electorate at the next election.
The Dublin Central TD was responding to the latest Sunday Independent/Millward Brown opinion poll, which shows an increase in support for both Fine Gael and Sinn Féin at the expense of the Independents.
Ms McDonald said she supported the assessment that the next election will be a toss-up between her party and Fine Gael. "People next time out will either choose the same old same old in Fine Gael or Fianna Fáil - that kind of politics. Or people can opt for a different politics and say: 'You know what, we want a different kind of government'," she said.
According to the opinion poll, Sinn Féin is the most popular party, having seen its support increase to 26pc.
Fine Gael is on 25pc, the poll shows, after the party secured a three-point rise.
Fianna Fail remained unchanged on 16pc, while Independents saw their support fall by a significant nine points.
Yesterday, Health Minister Leo Varadkar said Enda Kenny would be Fine Gael leader "for as long as he wants to be".
Mr Varadkar was responding to a separate finding in the opinion poll that 72pc of people believe his decision to come out as a gay man will not damage his chances of becoming Taoiseach.
Asked if he believed the next election will primarily be a battle between Fine Gael and Sinn Féin, Mr Varadkar said nothing could be taken for granted.
"The election is a long way away, and a lot can change between now and then. The most recent poll indicates that Fine Gael support is rising again and Sinn Féin is also very strong," he said.
"But I remember six months out from the last general election, the Labour Party was in first place," he added.