Labour has not ruled out working with Sinn Fein in government, calling on left-leaning parties to join forces in voting pacts as the general election campaign gets underway.
While Labour hopes to at least double its Dail seats to at least 14, Sinn Fein admitted it would try and consolidate its huge gains from the last election in 2016.
The Social Democrats also said it was targeting between five and eights seats.
Smaller parties are scrambling to make ground and gain attention amid the political jousting between the two main parties, Fine Gael and Fianna Fáil.
While many are promising alternative housing and health policies, the question of coalition options after the general election dominated the opening day of the campaign.
Labour leader Brendan Howlin, when asked about working with Sinn Fein in government, said he did not know, but he did not rule it out.
Nonetheless, Mr Howlin, even when pressed by reporters, failed to rule out working with Sinn Fein after the general election. Labour and the Greens are the only parties so far to include the option of working in power with Sinn Fein.
Mr Howlin reiterated that he wanted to build a “progressive” left platform, and encouraged Labour voters to give their second, third and other preference votes to like-minded parties, such as the Greens, the Social Democrats and Independents.
“I think we can have a critical mass in the Dáil if people do that. I think there will be a lot of flowing of transferable votes in the next Dáil because people have seen the rise of the discorded right.”
Labour is running 31 candidates but hopes to return at least 14 seats, up from its current tally of seven.
Meanwhile, Sinn Fein leader Mary Lou McDonald said she hopes the party will make gains over its 23-seat tally in 2016. While this now stands at 22 and after a recent by-election win, a number of popular Sinn Fein TDs will not seek re-election. These include Jonathan O'Brien, former party leader Gerry Adams and Martin Ferris.
Ms McDonald pledged that Sinn Fein, fielding 40 candidates, would run a “vigorous campaign”.
Starting her first general election campaign as leader, she added: "Despite improvements in the economy and more people back at work, people have less money in their pockets than three years ago.