Chile goes to the polls this weekend in the most important election since 1970. For the first time since the return to electoral politics in 1990 it looks as if the political and economic model inherited from the dictatorship is under threat.

Chile, for so long a poster-child for neoliberalism, has in recent years seen its chickens come home to roost. Frankly they are creating a mess. Workers, indigenous people, students, environmentalists and human rights activists have all mobilised on the streets in a vast new movement for change.

The old centrist coalition that oversaw the transition to a very limited form of democracy is no more. The right, which is in government at the moment, has seen its electoral support plummet.

Today it looks as if it might even slip into third place behind an independent candidate with no party backing. If so it would be the right's worst showing since 1964.

The political centre appears to have shifted significantly the left's way. Yet this isn't translating into party allegiances as in the old days. Together with a new voluntary voting system where all Chileans are automatically registered to vote, this means that there is a significant margin of uncertainty.

Two main coalitions face off in this election, the New Majority coalition led by Michelle Bachelet, the popular former president, and the Alliance, a right-wing partnership represented by Evelyn Matthei - the daughter of one of Pinochet's generals.

There are seven other candidates, including four who have broadly left-wing agendas. According to recent polls Bachelet will be very close to winning in the first round of the presidential elections and there are high hopes that in the simultaneous binomial parliamentary elections the New Majority coalition will be able to knock out a large number of right-wing candidates thanks to strategic left-centre candidacies.

The coalition's main hope is that Bachelet wins in the first round and that they manage to achieve a large majority in both chambers of parliament.

A victory of this magnitude would be necessary to enable the implementation of significant political reforms. Under the constitution left by the dictatorship, education, the binomial electoral system, copper-mining and various other areas are not under normal legislation and in order to change the laws affecting them either a two-thirds or three-fifths majority in both chambers is necessary.

Hence the urgency of this electoral process. Several of the candidates promise constitutional reform. Bachelet will most likely win the elections, but will her New Majority coalition win enough seats in Congress to be able to push through the reforms Chilean society is clamouring for?

On paper the New Majority should be more than capable of achieving this feat, being the type of broad coalition Salvador Allende would have dreamed of. It contains the Communist Party, the various socialist groups, Radicals, some new groups that have grown out of the social movements and the Christian Democratic Party. Yet this very breadth is also what makes it controversial for some potential voters.

For 20 years Chile was run by the Concertacion coalition of socialists and Christian Democrats. They accepted Pinochet's 1980 constitution and the maintenance of his economic system in return for civilian rule.

Many Chileans accuse them of overseeing the demobilisation of the social movement that forced Pinochet to step down, the entrenchment of the neoliberal model and the violent repression of the Mapuche indigenous people, all while doing little to address inequality or the dictatorship's abuses.

Because of this, for some left-wing Chileans the New Majority is seen as an expanded Concertacion, a coalition that will inevitably betray the hopes of ordinary Chileans.

For these Chileans 20 years of "democracy" has bred a deep distrust of institutional politics. For this reason the 2012 municipal elections saw 60 per cent abstention and recent polls have shown 80 per cent of Chileans no longer identify with a political party.

For many the Christian Democrats and the other former Concertacion parties are power-hungry opportunists, and the Communists and others are so desperate to be included in the political system after years of exclusion that they are ready to sacrifice the interests of the people.

Yet it is highly likely that most Chileans will vote in the upcoming elections. In presidential primaries held in June turnout was surprisingly high. Bachelet swept the board, winning three out of four votes.

Today polls show she is only four or five percentage points from winning in the first round with a substantial group of undecided voters to be won over.

The New Majority coalition contains several outstanding leaders of the recent student mobilisations and other leaders from the social movement and the unions. Their inclusion shows the pull that traditional politics maintains, despite the anti-institutional rhetoric of some left-wing groups.

The fact is that those who oppose the New Majority have no alternative method for achieving the reforms most Chileans want. In effect their disagreement with the New Majority lies in the legitimacy of an alliance with the old parties of the Concertacion.

Yet if reforms are to be carried through institutionally, then victory needs to be achieved on the unfair playing field that was accepted in 1989.

It is a dilemma that has crippled the Chilean left until now. Only a broad alliance for change can hope to win.

The bigger the victory, the more changes will be possible and the more marginalised the right wing of New Majority will be.

This is not a rerun of the 1970 elections with Allende at the head of a coalition for revolutionary transformation. This is the moment when Chileans can finally begin to dismantle the institutions left over by the dictatorship, making Chile a more democratic country with the right institutions to face the next cycle of history.

The broad avenues Allende spoke about on September 11 1973 aren't open yet, but these elections just might allow Chileans to finally break through to them.

Victor Figueroa Clark is the author of Salvador Allende: Revolutionary Democrat and a Latin America specialist based at the London School of Economics. He will be speaking at the Latin America Adelante! Conference on December 7 - see www.latinamericaconference.org.uk for tickets and details or follow on Twitter @latinamerica13.