Election year in France is an intense business: the French go to the polls on Sunday for the fourth time in two months. First, there were two rounds of the presidential election, in April and May, then last Sunday was the first round of parliamentary elections, which conclude this week.

New president François Hollande is hoping to win a majority in the national assembly for his Socialist Party government under prime minister Jean-Marc Ayrault. But the soap-opera atmosphere of the Sarkozy era seems to be continuing, as France has been transfixed this week by a spat between Hollande’s current girlfriend, Valérie Trierweiler, and his former partner (and mother of his four children) Ségolène Royal.

Royal is again running for a seat at La Rochelle in her home region, having been in parliament before her 2007 presidential bid. She is officially backed by the Socialist hierarchy, including Hollande and party secretary Martine Aubry (who beat Royal for the job in a particularly acrimonious ballot in 2008). But on Tuesday Trierweiler tweeted her support for the independent socialist, Olivier Falorni, who is opposing Royal in the run-off.

The Socialists, understandably enough, are furious at the distraction. While there’s not much doubt the left will win an overall majority, Hollande wants as many seats as possible for official Socialist candidates so as to avoid having to rely too much on dubious allies like the Left Front — or, for that matter, dissidents like Falorni. Instead, they find the President’s love life dominating the headlines.

Royal’s predicament should be easy for Australians to appreciate, because the French electoral system is fundamentally similar to ours: the two rounds approximate to the effect of preferential voting. Royal led with 32.0% in the first round to Falorni’s 28.9%, but the centre-right candidate had 19.5%. Le Monde has detailed results for those who can navigate a little French.) In the second round, those centre-right voters are quite likely to sow maximum dissension in their opponents’ ranks by turning out and voting for Falorni.

The usual drawback of two-round voting (apart from the extra cost) is that in a large and evenly spread field a strong third-place candidate who might have got up under a preferential system gets eliminated, leaving two finalists that the majority are unhappy with. That’s what happened last month in Egypt’s presidential election.

But France has a refinement to deal with that. In addition to the top two, other candidates can go through to the second round if their vote is more than 12.5% of the total enrolment — which, given the low turnout, works out at about 22% of the vote. If no one withdraws, three candidates can potentially fight it out in the run-off.

On Sunday there will be 34 of these three-cornered contests, or “triangulars”, most of them involving the far-right National Front. The National Front won 13.6% of the vote in the first round, but single-member districts make it almost impossible for isolated minor parties to win seats — the same problem that the Greens have in Australia. At best, the National Front will end up with four or five members in a lower house of 577.

The centre-left’s policy is to withdraw its candidate and support the centre-right in “republican solidarity” if they have a better chance of beating the National Front. The centre-right, on the other hand, maintains “neutrality” between far-right and centre-left. One centre-right candidate, Roland Chassain in Arles, withdrew from his “triangular” and endorsed the National Front; he now faces expulsion from his party.

One of Hollande’s election promises was to move to introduce an element of proportionality into the electoral system (last used in 1986). Fear of giving influence to the far right will probably make some of his supporters think twice about that idea. But the fact that the Socialist Party is within sight of a majority in its own right despite only winning 29.4% of the first-round vote suggests that reform is badly needed.