Power couples, like Malcolm and Lucy, always generate considerable interest and curiosity. Earlier this year The Canberra Times ran a feature story on Canberra's top 10 such couples. It featured a mix of public and private sector couples, headed by Peta Credlin and Brian Loughnane. That couple's careers have since come crashing down, caught up in the travails of former prime minister Tony Abbott, whom they both served though in different types of jobs, she as his chief of staff and he as federal director of his party.

Sometimes, as has been the case with the Turnbulls, reporting of the deeds of such couples is headlined by the phrase "two for one", implying that in the case of an elected public figure, like the Prime Minister, the public is getting both partners not just one. "Two for one" was regularly applied to Bill and Hillary Clinton when Bill was US President.

But this phrase needs to be used with care. It is either a truism, in the sense that all couples work together to some extent, or a dangerous concept. At the centre of the danger is the perception of conflict of interest. One consequence is that power couples in the Commonwealth Public Service have to keep out of each other's way, sometimes at some cost or at least disturbance to the career of one of them. Barriers have to be built between their careers or people will start to talk.

When partners are both prominent in the elected/appointed public sector congratulations for their individual achievements are also hedged about with reservations about the dangers of conflict of interest. In the case of the Turnbulls, the NSW Opposition Leader Luke Foley warned that Lucy Turnbull faced a challenge, which was to become "a champion for Sydney, never an apologist for Canberra"; and an unnamed Victorian state Labor minister, while admitting that Lucy was a "natural fit for the job", also expressed the hope that "there will not be any question of conflict".

When one partner is in the private sector, as Therese Rein, the wife of Kevin Rudd, was at the time of his election in 2007 issues of perception of conflict of interest also arise. Rein, almost as public a figure as Lucy Turnbull, was affected adversely. It was she who had to rearrange her business affairs. She did this largely by staying in the same employment services business but moving it offshore to Britain. She did this very successfully, but there was still a personal cost.

In one sense all this is most unfair to the partner who has to rearrange their affairs and even their career. It encapsulates a very modern dilemma. In regards to Lucy's new position the executive director of the Property Council of NSW expressed the commonly felt exasperation that two married people deserved to be treated as individuals whatever they chose to do. Glen Byres expressed the common view in this way: "The idea that neither Lucy nor Malcolm can make up their own minds does them both an injustice."

That is true but it also neglects the fact that conflict of interest is about both perception and reality and perception may be clouded by envy and/or politics. Power couples have to be very careful. The non-elected person in a partnership like the Turnbulls can come to be criticised as a way of getting at the elected partner.

This can happen even with the "non-powerful" partner of a couple in public life. It certainly happened to Julia Gillard's partner, Tim Mathieson, who had to put up with some extraordinarily personal innuendo, as well as criticism when he tried to do something himself in public life. Margie Abbott escaped that to a large extent, but her demeanour was still scrutinised incessantly for clues about her husband, the Prime Minister.

There are sacrifices and expectations for couples when one is an elected leader. Invariably, whatever their own career, the partner of the elected one is expected to play a public role on certain formal governmental occasions as well as the inevitable political occasions, such as election campaigns. This eats into other things they would like to do, but it can also bring enjoyable opportunities as Hazel Hawke used to say of her life with Bob when he was prime minister.

Beyond that, a loving partner like Lucy, who has shared all the ups and downs of her husband's career and worked side by side in much of it, will want to assist him. She will want to be alongside him when things are going well, but even more so when they are not going well, as will surely be the case sometimes. She was right in the thick of it during his worst moments as Opposition Leader.

There is no easy answer for couples in public life, whether they are so-called power couples or more traditional couples. However much they try to lead separate lives neither the media nor some members of the public will allow it. That is one of the sacrifices of public life, accompanying the many benefits. Couples just have to be resilient and stick together.

John Warhurst is an emeritus professor of political science at the Australian National University.

John.Warhurst@anu.edu.au