Catherine Connolly is running as an independent candidate with the support of a broad base of left-leaning parties and politicians, including the main opposition party Sinn Féin.
The coalition government party, Fine Gael, is represented by a former government minister, Heather Humphreys, who comes from a Protestant community in the border county of Monaghan.
A third candidate, Jim Gavin, who was selected by the main coalition party, Fianna Fáil, withdrew from the campaign earlier in October after intense controversy over a 16-year-old rental dispute in which he owed €3,300 (£2,870) to a former tenant.
