The Fianna Fáil leader has said Sinn Féin has "no realistic chance of being in government" despite the party's strong performance in opinion polls over the weekend.
Micheál Martin made the remark as the campaign enters its final few days, adding that he is confident that his party will outperform the latest opinion poll, which indicated that support for his party is strong at 24%.
The Business Post/Red C survey indicated that support for Fianna Fáil and Sinn Féin is neck and neck, just days before voters go to the polls.
It said support for both parties is 24%, a drop of two points for Fianna Fáil and an increase of five points for Sinn Féin. It leaves Fine Gael flagging in third place on 21%, down two points.
However, despite the poll showing little difference between some of the parties, Mr Martin believes Sinn Féin has "no realistic chance of being in government" because of the number of candidates it is running.
Mr Martin said he is confident that Fianna Fáil will "outperform" the poll.
"We are in a strong position", he said. "We believe, given the numbers we are running up for candidates, that we are the only party with any realistic opportunity of leading an alternative government and giving the people what they want, which is a change of government."
He expects further polls and "different shifts" in the days ahead.
"We're concentrating on our poll and we're quite satisfied where we are in terms of leading into the campaign," he said.
I think we will outperform that particular poll because of the strength of our candidates and I think we've been a very strong position to gain seats.
Mr Martin said the opinion polls are framing "every conversation" but said other parties will be confident of picking up seats too.
Asked if Sinn Féin's performance in the poll would make him reconsider his stance on a potential coalition, he responded that it "doesn't make any difference, to be quite frank."
On Tuesday, Mr Martin will debate Taoiseach Leo Varadkar in RTÉ's leaders' debate. Sinn Féin's strong polling has added further weight to the calls that Mary Lou McDonald should also be included but Mr Martin said Sinn Féin has "no realistic chance of being in government" because of the number of candidates it is running.
Sinn Féin is running 42 candidates in comparison to Fianna Fáil's 84 and Fine Gael's 82.
He said the debate was about the two candidates who have a chance of leading a new government putting themselves before the people.