As Labour prepares to defend its Tooting seat on Thursday, in the by-election triggered by Sadiq Khan’s resignation of his Commons seat, LabourList reporter Sarah Pine went to meet the woman who aims to fend off the Tory challenge in south London.

Dr Rosena Allin-Khan, Labour’s candidate in Tooting,is up against some strong challenges, but the campaign is hers to lose. Spending the day with Allin-Khan and her team on the campaign trail shows me she knows what she is doing in this race.

The campaign has, sensibly, aligned her with Sadiq Khan. Rosena tells me Tooting residents are “really excited” about seeing their local boy in City Hall. The pair appear together on campaign materials and I overhear her speak positively about Sadiq’s victory on the doorstep.

She has a similar message to Sadiq, which draws upon the fact she is local, the daughter of two immigrants, Muslim, and grew up poor – but working hard and succeeding in a prestigious profession. She talks about her upbringing and thinking she could never be a doctor because she didn’t share the background of those she saw succeed.

“I‘m the daughter of immigrants. My dad’s Pakistani, my mum’s Polish – but I’m 100 per cent Tooting. My mum worked in the petrol station on the High Road. My dad wasn’t a bus driver but we do say perhaps Sadiq’s dad drove his bus into my mum’s petrol station. My dad actually fixed TVs in Furzedown, which is in the constituency.

“But life growing up got really tough – my mum worked three jobs to put food on the table and she ended up raising my brother and I on her own. It was tough.

“I’ve always wanted to be a doctor since I was three and I found out my grandma was blind. When I was in school I was led to believe people like didn’t go on to become doctors. It was with the support from my mum with all her messages about her hard work and social justice that I went on to study medicine.”

When we talk she ties together her plans with those of Khan’s – saying she wants to work with City Hall to build more housing in Tooting and to bring Crossrail 2 – the huge new line linking the northern and southern suburbs of London – to her area. She’s also learnt the positive messages from the Mayor’s campaign and has pushed hard on themes such as her commitment to the NHS, childcare and social mobility.

“I think Sadiq’s successful mayoral campaign shows what the Labour Party can do when we’re united and come together as the Labour Party family – and that’s what we’re doing in this campaign,” she tells me. “I’m all about building bridges – just like Sadiq has done.”

She doesn’t go in for bashing other candidates or comparing herself to them – which would be easy for such an accomplished woman.

Rosena is an A&E doctor, a councillor, a mother of two young children and a Cambridge graduate. She’s charismatic, likeable and knows how to communicate with the public. She is recognised from her time in local government and her campaign is good at drawing on this.

All of the above comes across in her work on the doorstep. The reaction from voters seems positive, not least because Rosena is good at talking about local schools, cafes and landmarks.

Yet there are structural challenges the Labour candidate faces. The party’s 2015 majority in Tooting was fairly slim – 2,800 votes – and turnout is historically low in a by-election. Factors on the day, such as bad weather or bad political news, can have an impact.

The Tories increased their share of the vote in 2015, but this came from the collapse of the Lib Dem vote – and Labour ended up increasing their share by a small amount more. The Liberal Democrat vote went down to around 2,000 from 7,500. This looks unlikely to decrease any more and may even rally a small amount with the party’s recent efforts in the May elections.

There is a lot of potential confusion with the EU, though local campaigners are confident voters are aware they are needed for two separate polling dates. London’s pro-EU bias means she is in-step with the voters, though her Conservative rival has not made the same mistake Goldsmith did and has also said he supports a Remain vote.

Yet voter fatigue could impact turnout, meaning Labour voters targeted in the remaining weeks tune out of their local contest.

Ultimately, the referendum is probably a positive in the campaign. If the by-election was at another time, it’s likely the Government would look a lot stronger and Labour would face an uphill battle against a Conservative Party dominant nationally. Currently the Tory splits over the EU are making them look less competent, and Labour is comparatively united at the moment.

Nationally Labour isn’t polling high enough to deliver the sort of sure win we saw there when Labour took the seat in 1997. Our performance across the country means we cannot rely on a strong national brand deliver a bonus in Tooting.

Rosena Allin-Khan has, however, responded to this well – learning the lessons of her predecessor and keeping the campaign separate from national Labour politics, lessening the impact of Corbyn, who generally doesn’t appeal to Tory swing voters.

Most notably, last month’s mayoral election saw almost twice as many voters chose Khan over Goldsmith – 18,653 to the Tory’s 9,481 – so the campaign’s association between the two Labour politicians is a shrewd move that would capitalise from the seat’s rejection of the Tories last month. Her campaign team tell me about just how badly the Tories’ racially-charged campaign went with the local diverse electorate.

Dan Watkin, the Conservative candidate, does pose a significant challenge. He has a strong local presence and commanded a strong performance in 2015’s election.

While Tooting is in London, it is more suburban than much of the city, and borders Tory seats Battersea, Putney and Wimbledon. The borough council – which also covers areas further into the suburbs – is Tory-controlled and looks likely to stay that way.

Rosena Allin-Khan is doing this campaign right. She’s up against a strong opponent, but knows how to win this by-election. A loss isn’t impossible, but the mood on the ground gives us reason to be optimistic.