AUGUSTO PINOCHET left the scene as Chile’s dictator 25 years ago, but the electoral system he bequeathed has governed politics ever since. Under the country’s unique “binominal” system, each parliamentary constituency has two seats; the winning candidate takes one and in most cases the runner-up takes the other. This has reserved nearly all the seats in parliament for two big coalitions, the centre-left New Majority (to which the president, Michelle Bachelet, belongs) and the centre-right Alliance.

The system has brought Chile stability at the expense of diversity. It kept small parties out of parliament unless they joined one of the two big coalitions, and ruled out landslide victories by either side. Moreover, it has tended to over-represent the Alliance at the expense of New Majority. Rural areas, which had supported Pinochet, were given more weight than their populations warranted.

Politics in Chile is about to get messier and more interesting. After numerous failed attempts, the ruling New Majority has mustered the votes to scrap the binominal system; the measure passed both houses of parliament in January and should become law soon. Under a new system the number of lower-house constituencies will be cut from 60 to 28. Each will return between three and eight candidates, depending on its population, to be chosen by proportional representation. In some constituencies small parties will be sure of winning a seat with just 13% of the vote. The system applies to the Senate, parliament’s upper house, as well. Some constituencies will now return five senators rather than two.

The new voting system promises to end what Ms Bachelet has called the “permanent draw” between left and right, which has bred complacency among politicians, produced weak majorities for governments and turned off voters. Less than half of the electorate bothered to vote in the last election. The new system may cause political fragmentation, which in other countries has made coalition-building and governing difficult. Its backers reckon that making the legislature more representative is worth the risk.

As well as adding ideological diversity to parliament the reform is also supposed to bring in more women: at least 40% of the candidates fielded by parties will have to be women. Now just 16% of deputies and senators are female.

Ms Bachelet’s foes complain that when the permanent draw is broken the main winner will be her New Majority coalition. It is also possible that it will break up as smaller groupings seek electoral success on their own. Cynics say that the candidate quota for women is unlikely to do much good; they expect parties to dispatch female candidates to their least winnable constituencies.

Non-politicians have pounced on another aspect of the reform: it will increase the number of elected politicians. The number of lower-house deputies will rise from 120 to 155; there will be 50 senators rather than 38. Many Chileans, disgruntled with the ruling elite, want fewer politicians, not more. One online commentator grumbled that the reform will just mean “more clowns for the circus.” Its authors hope that Chile’s more vibrant politics will prove him wrong.