As if the future was not hair-raising enough, Ireland woke up on Wednesday morning knowing that Mary Coughlan was running the country. Thanks a lot, China.

At a time when political leadership was required like never before, the Taoiseach departed for Shanghai, leaving a deputy in charge who insists on overloading Paris and Berlin with Euro commissioners and thinks 86 plus 30 equals 100. Hard to believe that only six months ago, her supporters chaired her on their shoulders across the county border from Leitrim into Donegal, whooping triumphantly, while one commentator tut-tutted as if she had returned from the county fair with the prize for best pig. "Mary One Step Closer to Becoming Taoiseach," crowed the local paper. That was some night alright for old-style how's-she-cuttin' pump politics. As the bonfires burned across southwest Donegal, the newly invested Most Powerful Woman in Ireland promised: "I'll be doing my best for the people of the northwest, particularly my own county."

Her voters will be reminding her of that pledge as local controversies continue to flare up from the Budget. A Donegal solicitor has already offered to mount a High Court challenge to the planned move of 265 military personnel from army barracks in Lifford and Letterkenny to Finner Camp in Bundoran, claiming it will cost the local economy €6m. Coughlan is also coming under attack in the constit­uency over cutbacks in education, health and local authority spending. Fianna Fáil councillors in Donegal held a meeting last Monday and formally opposed any attempt to increase water charges or commercial rates to make up for lost funding. Earlier, in July, the party's elected representatives in the county met the Tánaiste to warn her their candidates were facing humiliation on the doorstep at next June's local elections over inadequate cancer services.

The kindest of her critics say Mary Coughlan, the daughter and the niece of her two constituency forerunners, has been a disappointment. Others argue she is a mis-appointment, plucked from cabinet backwaters to form the state's axis of power. "Well, I hate to say it," said a friend and convert to the growing band of Coughlan critics, "but she was promoted because she was female".

As Fianna Fáil experiments in gender-alignment go, appointing Mary Coughlan Tánaiste was an audacious decision by Brian Cowen. It seems to have been an idea fermented in his mind long before he became Taoiseach in May. Around this time last year, while Bertie Ahern was locked in his early encounters with Mahon, some of Cowen's senior supporters were noticeably talking her up, citing her track record in the Department of Agriculture and her winning performances on television. Cowen, they said, thought she was "a great girl". She was one to watch.

Watching Mary Coughlan has become as voyeuristic a pastime as watching Ricky Gervais in The Office. No sooner had she become Tánaiste and Minister for Enterprise, Trade and Employment than she put her foot in it over the Lisbon Treaty. Not once, but twice, she erroneously iterated that the bigger EU member states were entitled to two commissioners apiece. The blunder was all the more unexpected coming from a minister with extensive experience negotiating for farmers at EU level. After that, she quietly withdrew from the government's doomed Yes campaign.

In the post-budget turmoil, her despotic tactlessness proved provocative when she warned her party backbenchers it would be "disrespectful" to their leader if they were to publicly criticise the abolition of over-70s medical cards while Cowen was in China. Talk about salt in the wounds of backbenchers already bristling at not being consulted in advance about the harshest budget most of them had ever been required to justify to their constituents. In his resignation letter to Cowen, the new Independent Joe Behan wrote: "I found that warning to be insulting in the extreme". Behan had not even composed his letter when Coughlan was giving a maths lesson to the Dáil in relation to the pension card. "I ask for the indulgence of the House, given that we need clarity on this issue," she said. "Of the savings of €100m, €86m is for GPs and €30m is for pharmacists."

Mary Coughlan shot to national politics following the death of her father, Cathal, in 1986. He had inherited the Dáil seat when his brother Clem was killed in a car crash en route to casting what was widely predicted to be a crucial vote in a Fianna Fáil heave against Charlie Haughey's leadership in 1983. The young, personable social worker was instantly popular in Leinster House where her status as "the wee Donegal lass" would become both an advantage and a detriment.

Twenty-one years on, the 43-year-old is still widely liked. Critics of her political performance visibly cringe as they catalogue her faults and rush to add how amenable and amiable and "not stuck up" she remains. This seemed borne out within days of her elevation. Dáil microphones amplified remarks the Taoiseach made to her sotto voce in the chamber after Labour leader Eamon Gilmore had rebuked the National Consumer Agency for failing to act on rising health costs. "We need to get a handle on this," Cowen said to his right-hand woman. "Will you ring those f**kers?"

The farmers' lobbies loved her, not only for the €8.7bn she wrestled for agriculture from the National Development Plan before last year's election, the 60% grants she secured (70% in border counties) under the Farm Waste Management Scheme and the €80-per-cow suckler scheme. Their bible, The Farmers Journal, recalled in a valediction last summer: "The buzz when she worked the room at conferences and meetings was palpable." But one farmer who saw another side to her remembers: "She's not a lady to cross. She'd eff you out of it better than any man."

Mary Coughlan has done herself no favours but she has also been the subject of blatant gender stereotyping. When she was first promoted, her figure and her dress sense were tediously analysed in some newspapers. The high point of media coverage was a Saturday-night tv chat show in which she discussed how her garda husband, David Charlton, lost a leg in a traffic accident and how her son was born profoundly deaf and how she managed to juggle her busy life and stay slim. Last week, Fine Gael's favourite upstart, Leo Varadkar, dubbed her Ireland's Sarah Palin, letting the inescapable dumb-blonde insinuation hang suggestively. Male colleagues who have exhibited no greater possession of grey matter in recent weeks have not been subjected to such pigeonholing. One suspects it has nothing to do with the fact that they are natural brunettes. Or were, once upon a time.