Terrific members of the Liberal team don’t whinge and walk from a marginal seat - they stay and fight. Resignation letter is a job application to ABC Green Left - Julia is the reason why you are losing. Forget bullying in your workplace and focus on lifting wages for Australia.— Ross Cameron (@RossCameron4) August 29, 2018
Strange way to declare your intention to fight. Still, it is not a career for conscripts. RT Lib MP quits over Turnbull spill https://t.co/DBo9ZU7G2p— Chris Kenny (@chriskkenny) August 29, 2018
Ms Banks was the only federal Liberal to win a seat from Labor at Turnbull's 2016 union corruption-busting double dissolution election.
It's a key marginal seat - wikipedia tells us:
The Division of Chisholm is an Australian Electoral Division in Victoria. The division was created in 1949 and is named for Caroline Chisholm, a social worker and promoter of women's immigration. It is located in the eastern suburbs of Melbourne, and includes the suburbs of Ashwood, Blackburn South, Box Hill, Burwood, Chadstone, Huntingdale, Mont Albert, Mount Waverley, and parts of Clayton, Forest Hill, Oakleigh and Surrey Hills.
On its original boundaries, it was a comfortably safe Liberal seat centered on Camberwell. However, successive redistributions from 1980 onward have moved the electorate south-east, taking in strongly Labor-voting suburbs to balance out the relatively affluent Liberal-leaning suburbs in the north of the seat, and making the seat marginal. The first member for Chisholm, Sir Wilfrid Kent Hughes, was one of Australia's most distinguished soldiers and a former Olympian, who held the seat until his death on 31 July 1970.
Labor finally took the seat in the 1983 landslide that brought Bob Hawke to power, only to lose it in 1987. Anna Burkebecame the second Labor member ever to win it in 1998 election and held it until her retirement in 2016. Julia Bankswon the seat for the Liberals at the 2016 election, becoming the only Liberal challenger to take a seat off Labor at that election.