That's because there are three councillors elected on the Green Party ticket and three on Labour's.
Former deputy mayor Jill Day and new councillor Tamatha Paul have strengthened the ranks.
Returning councillors Iona Pannett and Fleur Fitzsimons had been tipped as options from the left for the deputy mayor role.
But Free has emerged as the frontrunner.
Pannett and Fitzsimons are strong personalities who could clash with Foster.
Free on the other hand is seen by some on the left as more pragmatic and a better fit for the role.
Free has spent six years on Wellington City Council.
She held the public transport, cycling and walking portfolio during her most recent term.
In her local body election profile Free said as a councillor she had listened and worked collaboratively to get results.
"I've led the rollout of new cycleways and walkways and championed initiatives such as the predator-free projects and Kilbirnie stormwater upgrades."
She has an engineering degree and Masters in Public Health.
Campaigning for the Eastern Ward, she said continuing work to ensure the regional council sorted out the new bus network rollout was an "absolute priority".
Other priorities include better transport to reduce congestion and emissions, getting the central library back open, safer walking and cycling, housing and a focus on water infrastructure and coastal protection.
