In a political world dominated by grey men in grey suits, Iris Robinson – the wife of Northern Ireland's first minister Peter Robinson, and an MP and MLA in her own right – has always stood out. Not, it must be said, because of any particular acumen or brilliance ("I recognise I'm not the brightest light in the chandelier when it comes to debating constitutional issues," she admits, "I leave those to Peter") but because she has always lived as though she is performing herself in the melodramatic movie of her life.

That's why the revelations about her extramarital affair, her abrupt departure from politics and her attempted suicide – while grim and painful for the politician and her family – don't seem particularly surprising to seasoned Iris-watchers. Unlike her husband Peter (seemingly a model of stony-faced repression, despite his spiky, incongruously boyish haircut and jolly ties) Iris is emotional, loud, flamboyant and glamorous, a kind of Ulster Sarah Palin, and the very antithesis of the buttoned-up unionist matron. She charges about in her convertible Mini Cooper, leaving a cloud of perfume and gifts from grateful constituents trailing in her wake. Yet you sense that she is always watching herself being watched, creating a persona for herself in the same way she interior-designed her home, with its opulent Tuscan bathroom and four-poster Gothic bed.

But Iris is no maverick. While she has evidently relished the sexy granny look, she is every inch an evangelical Christian (of the Pentecostalist, rather than the Free Presbyterian variety). Martin McGuinness and Gerry Adams are on her prayer list – "I'd like to see them redeemed by Christ," she said in one interview. More recently, she's been airing her stridently fundamentalist views, most notably when she referred to homosexuality as "an abomination", and offered to put gay people in touch with a wonderful psychiatrist of her acquaintance who would sort them out in no time. "The government has a responsibility to uphold God's laws morally," she added, for good measure.

Now that the Scarlett O'Hara-inspired facade has crumbled, sympathy for her has been tempered by these outbursts. There's a sense among some people (mainly those bruised by her former attacks) that, in recklessly mixing personal morality with politics, Iris has little right to expect non-judgmental understanding now.

But, politically speaking, it's wrong to assume that the sex scandal will finish off the Robinsons among the evangelical Christians who make up so much of the DUP vote. The revelations can be seen as in keeping with their world view. Many Ulster evangelicals have an ingrained mistrust of what they see as women's vicious, conniving, sexual ways. In this view, evangelical women must still enact the story of poor, crazy Eve: weak, in need of male supervision and control, easy prey to temptation and deficient in moral capacity. So Iris seemingly fits in neatly there. Meanwhile, Peter Robinson stands free and clear as the wronged husband, grieved and dignified in his study, alongside a card from his children saying what a great dad he is.

No, the real harm to the Robinsons, if it comes at all, will be about money, not sex. It has been alleged that the public confession may have been in part prompted by a BBC investigation into Iris Robinson's finances.

If there is impropriety there, that's the "sin" that would really stick in the craw of the canny but upstanding Protestant businessman voter – and prove the true undoing of the Robinson name.