If the PDs successfully portray themselves as the defenders of the small guy against big powerful interests, this attitude could leave Labour on a very sticky wicket if they are seen as the protectors of the semi-state big boys (airport, CIE etc) and the public sector unions.
In 1992 Labour made the big mistake of ruling out coalition with Democratic Left for some obscure reason and instead jumped into bed with FF. (btw, I would suggest that Labour, and the country in general, have yet to recover from the consequences of this error). In the meantime the same Democratic Left personnel that were in situ in 1992 have become respectively Leader, Deputy Leader and President of Labour!