Not because they'll lose the seat - it's one of the Conservatives' safest - but because the process for picking their candidate will indicate how vigorously David Cameron's new 'A list' will be enforced. You remember the list? A sort of ultra-mild version of Labour's all-women shortlist but sacrilege to many Tories nonetheless.
Fifty per cent women and 10 per cent ethnic, constituency associations are expected to pick their candidate from the list unless there's an exceptional reason not to. The upcoming by-election ties nicely with a poll of constituency chairmen More4 News has put together asking what they think of Dave's candidate-selection plans.
I spent yesterday trudging the streets of Bromley, brandishing cards to demonstrate the rationale behind the list. I say brandishing cards because I had three: three pictures of three people, a white man and white woman - senior programme editors here at ITN - and a black man ... who happened to be the Tory MP for Windsor.
What I was trying to see was who, all other things being equal, people would vote for. The woman won convincingly. When I asked those same people who they thought was already the MP, just 2 of 20 picked the woman. Twelve thought the white man while 6 correctly picked the (black) MP for Windsor. The Conservatives' problem in one easy gimmick: people want to vote for women, but they think all Tory MPs are smarmy white men.
You'd think such a gimmick would be the easiest thing in the world to carry off. Not in Bromley. Thrown out of Starbucks, thrown out of a shopping centre, we were almost thrown off the street. Two policemen approached and said we were "filming suspiciously". Quite how you film suspiciously I'm not quite sure but CCTV cameras had filmed the camera filming. All very Big Brother: in this post 7/7 world, I'm beginning to expect it.
Anyway, Cameron's reasons explained in Bromley, it was back to the office to try to get an interviewee for the post-film chat. After a series of telephone calls, I tracked down 'ex Corrie' star Adam Rickitt a couple of days ago, expecting him - a surprise on the list - to be the air-head he undoubtedly looks.
He wasn't. Let me say it first, here and now. Adam Rickitt has views on real issues and puts them eloquently. Nuclear power? He thinks it's sadly necessary. A European army? Not on his life. Peggy Mitchell? Oh, sorry, wrong soap. Sadly, while he had views, he didn't have time. Between call one and call two he suddenly got very busy "rehearsing 'till late late every night." In my piece, his looks will shine through. His views, though, will have to wait .
Other calls to other wannabe candidates reveal skull-duggery and conspiracy at the heart of the Tory party. Someone tells me of six Conservatives preparing a case to sue the party over the list. From two people I hear that this isn't really the top list at all. The really plum safe Tory seats won't come up this summer.
They'll come up when aging MPs decide they've had enough of elections. Then those on the secret A* list will be drafted on onto the A list: the danger otherwise is that a marginal could snap the real stars up and they'll have to spend their MP years out campaigning rather than governing, plotting or - I don't know - drinking. An important MP that needs to work for his seat? Perish the thought.