Sinn Féin is asking the party's 41 TDs and Senators to vote for Independent candidate Billy Lawless in the Seanad byelections.
Mr Lawless is standing for election to the Seanad’s Industrial and Commercial panel.
Fianna Fáil's candidate Gerry Horkan remains the favourite to win election to the panel. However, the decision by Sinn Féin to back Mr Lawless will boost the Independent candidate's chance of staying in the hunt for a seat.
It is a blow to the hopes of Lord Mayor of Dublin Hazel Chu, the Green Party chairwoman who is running as an Independent in the byelection for the panel, as well as to the chances of Labour Party candidate Ciarán Ahern.
A pact between Fianna Fáil and Fine Gael means their respective candidates Gerry Horkan and Maria Byrne are the favourites to take the two vacant seats on offer in the byelections. The vacancies have arisen in the Industrial and Commercial and Agricultural panels respectively.
However, it is a secret ballot and the possibility remains that some Coalition TDs and Senators may not vote for the agreed Government candidates.
Mr Lawless hopes that the support of Sinn Féin, Independents and some rebels from the Government parties will offer him a fighting chance of a seat, telling The Irish Times: “Otherwise it can’t be done.”
There has been an expectation among Sinn Féin sources in recent days that the party will issue guidance to support Mr Lawless due to his work with the Irish diaspora and support for extending voting rights in presidential elections to the Irish abroad and people in the North.
It's understood the issue has been considered by Sinn Féin's Ard Comhairle.
Galway native Mr Lawless ran a chain of bar-restaurants in Chicago but they're now run by his children and he has been back in Ireland full-time since last May. He was previously appointed to the Seanad by former Fine Gael taoiseach Enda Kenny. Mr Lawless sat in the Seanad as an Independent and has said he will do so again if re-elected.
A statement by Sinn Féin said Mr Lawless has a “track record in working with the diaspora, the undocumented in the US and in relation to presidential voting rights; which are priorities the party share”.
Ian Marshall, a unionist and former president of the Ulster Farmers' Union, is the party's preferred candidate for the seat on the Agricultural panel. Sinn Féin said: "It is important that the North has voices in the Oireachtas and that unionist perspectives are included in that; which is why we will be supporting Ian Marshall."
The party added: “We will not be supporting Government candidates or those who intend to take the Government whip.”
Fine Gael's Ms Byrne and Labour's Angela Feeney are the other candidates for the Agricultural panel.
The pact between Fianna Fáil and Fine Gael should see the two official Government candidates elected.
A total of 218 Oireachtas members are eligible to vote and if all of them send in valid ballots the quota will be 110. Ballot papers are being sent to the electorate on Wednesday and are to be returned by the morning of April 21st.
Meanwhile, the Green Party has been engulfed in a row over Ms Chu’s candidacy.
Party leader Eamon Ryan wanted his TDs and Senators to vote for Coalition candidates in the expectation that they would support a Green Party candidate should another vacancy arise during the lifetime of the Government.
Deputy party leader Catherine Martin on the other hand signed Ms Chu’s nomination papers and argued against a parliamentary party motion calling for Ms Chu to step aside as Green Party chairperson for the duration of the Seanad election campaign. In launching her campaign as an Independent, Ms Chu said she would “most likely” take the Green Party whip if elected as a senator.