The challenge by Fine Gael and Labour for the last seat and Liz O'Donnell's electoral vulnerability are the key political issues in the Dublin South five-seater.
The largely middle-class constituency is ruthless in its volatility - returning TDs to the Dáil only to dispense with them at future elections.
Twenty years ago, when the PDs were on a high, Anne Colley was elected in a bitter battle only to lose her seat at the subsequent election.
O'Donnell, who is now the party's deputy leader, did well to win back the seat in 1992 and has held it since. Any prediction that she might lose this time has to carry the political health warning that it has been wrong in the past. She might well confound the pundits again. But there is no doubt that she is one of the PD TDs under pressure, with the challenge by Fine Gael and Labour a bigger threat than last time.
Fine Gael once held two seats in the constituency, but that ended in 2002 when Alan Shatter was swept from the Dáil in the national swing against the party.
Labour has had mixed fortunes. Journalist and academic John Horgan won a seat for the party in the 1970s, while Eithne Fitzgerald topped the poll in the 1992 "Springtide", with over 17,000 first preferences, only to lose out in 1997.
It is against this background that the two parties are challenging this time, with O'Donnell's seat clearly the most vulnerable.
Fine Gael is running outgoing TD Olivia Mitchell, Shatter and Cllr Jim O'Leary, while Labour is running Cllrs Aidan Culhane and Alex White. The popular wisdom is that Mitchell, FF Minister for Social and Family Affairs Séamus Brennan, Chief Whip Tom Kitt and the Green Party's Eamon Ryan will hold their seats.
Mitchell is a formidable politician and is likely to be given a senior cabinet post if the party gets into government. Brennan and Kitt have secured their constituency base over the years, keeping a close eye on Fianna Fáil's third candidate, Glencullen councillor Maria Corrigan.
In any constituency with an opening for a Fianna Fáil TD, Corrigan would be a certainty, but she has suffered the fate of being the runner-up to two strong sitting FF TDs. In 2002, she polled 3,180 first preferences, and she is likely to do better this time.
Ryan is expected to benefit from the growing popularity of his party, particularly in urban areas. He polled 5,222 first preferences in 2002 and is likely to do much better this time, perhaps challenging Brennan, who polled 9,326 first preferences, for his place at the top of the poll.
Shatter has a track record in Leinster House, but O'Leary, with his endless enthusiasm for canvassing and his impressive poster campaign, is not to be underestimated.
Labour, meanwhile, may well have made a mistake in running two candidates. Culhane, who represents the Dundrum electoral area in DúLaoghaire/Rathdown County Council, and White, who represents Terenure/Rathfarnham on South Dublin County Council, tied at the selection convention.
Culhane was chosen when his name was drawn from a hat and he was very annoyed when White was later added to the ticket. The rivalry between the two is intense.
O'Donnell gained last time from Minister for Justice Michael McDowell's celebrated poster, in nearby Dublin South-East, warning against the dangers of single-party government. She increased her first-preference vote from 5,444 to 8,288. But matters are more problematic for the party this time.
The health services, including improved facilities for those with special needs, are surfacing on the doorsteps. There is also concern about the number of high-rise apartment developments, most notably in Dundrum. Traffic congestion and the extension of Luas lines to areas like Rathfarnham and Knocklyon are also exercising the minds of voters.