A diverting by-election looms in the Victorian state seat of Melbourne, former minister Bronwyn Pike evidently having made the not unusual decision that opposition is not for her.

This electorate is of course a dead zone for the Liberals, such that the parliamentary balance of 45 pro-government and 43 anti-government members is certain to go undisturbed. However, it offers a golden opportunity for the Victorian Greens to achieve what they have never quite been able to manage: victory in a state lower house seat.

Bounded to the south by the Yarra River, the electorate of Melbourne extends north through the city centre to the suburbs immediately to the north and north-west. The more easterly part of what is generally considered the inner-city constitutes the equally Greens-friendly seat of Richmond, and the two together constitute most of federal Melbourne.

The map below shows two-party Labor-versus-Greens polling booth results from the 2010 election, with the font size varying according to the number of votes cast. As you can see, only in one booth did the Greens score a two-party majority, that being the Carlton booth nearest to the University of Melbourne campus.

Electorally speaking, three tendencies can be observed within the electorate. About 60% of the voters are in the inner northern suburbs (together with the booths in the CBD itself, which are presumably used by many voters who don’t live there), where Labor and the Greens were each worth about a third of the vote and the Liberals roughly a quarter. In Docklands and East Melbourne, high-powered city centre types drive the Liberal vote well into the 40s, although these booths only count for 12% of the total vote.

The remaining quarter of the voters are in Flemington and Kensington which, being on the far side of the CityLink motorway, mark the beginning of Labor’s western suburbs heartland — albeit the gentrification of Kensington has complicated this picture in recent years. Flemington however remains high in public housing and low in median income, and the area collectively shares a voting pattern of weakness for the Liberals (barely 20%) and strength for the Labor (over 40%, and approaching 50% in Flemington).

Emphasising the point that the Greens are a very recent phenomenon in Victorian state politics, the party did not bother to field a candidate in Melbourne as recently at the 1999 election, at which Labor was worth 59.3% of the primary vote. In the wake of a breakthrough result at the 2001 federal election, the Greens well and truly had their act together by the 2002 state election, when the strength of their performance in the inner-city was the only complication in a picture of electoral triumph for Labor across the state.

In Richmond, Northcote and Brunswick as well as Melbourne, the Greens gouged double-digit shares of the primary vote from both major parties, overtaking the Liberals and landing short of victory by respective margins of 3.1%, 7.9%, 9.3% and, in the case of Melbourne, 1.9%.

This inevitably engendered high hopes for the party at the next two elections, but they were met both times with disappointment. A late-campaign publicity blitz by Labor in 2006 was credited with keeping Bronwyn Pike’s slender margin intact, and Labor also held its ground in Richmond. Then in 2010 came a disturbing development for the Greens, with the Liberals jettisoning their practice of directing them preferences ahead of last-placed Labor. This resulted in a comfortable 6.2% win for Pike, despite the primary vote gap between Labor and the Greens shrinking from 17.2% to 3.8%.