Micheál Martin has said that he is the only alternative to Enda Kenny for Taoiseach.
Fianna Fáil leader also said that he wants 'no holds barred' debate with Enda Kenny ahead of the election.
The Cork South-Central TD was speaking at the start of the party's two-day 'think-in' ahead of the return of the Dáil next week.
He claimed that Fine Gael are already attempting to hide the Taoiseach behind soundbites.
Asked if he was "probably the only alternative to Enda Kenny going for the next election", he responded: "Yes, absolutely."
"I think that is the bottom line in terms of the Taoiseach.
"I think what's interesting is that I've been watching the Fine Gael parliamentary party think-in from reading the very good reports that you've all filed, and it seems the fundamental strategy is to hide Enda Kenny as often as they can, in order to propel themselves to victory.
He added: "It will be up to the Taoiseach to come up front, and to debate publicly with me in relation to these issues," he said.
"And that we could have a fulsome, energetic and active campaign where political leaders don't just go for the sound bites or just running for the organised PR opportunities but that we have no-holds-barred debates with the Taoiseach and with others.
"And I'm up for that - I hope the Taoiseach is."