Labour's candidate for Mayor of London, Ken Livingstone, the former mayor - y'know the one before Boris bumbled his way into the job and then spent four years bumbling around not doing very much other than introducing Boris bikes (which weren't even his idea) and obliterating bendy buses - has a problem.
It's not that Livingstone loves newts, that's just a bit weird. It's not that he likes a drink and occasionally casually insults London journalists when drunk. I doubt many people would really mind him doing that, they probably wish they could insult a journalist or two when drunk themselves.
No, it's not even the fact that Boris supposedly got a big bounce in the opinion polls for an apparently expletive ridden nose to nose confrontation with the former mayor in a lift last week. That's not necessarily why Boris got the bounce in the opinion polls. Although what he said to Livingstone is probably what many a disgruntled Londoner may have wished they could have said to him.
Nope. As we all know by now - or at least all of us that live in London and give a toss - it's how much tax Livingstone pays.
This little drama has been playing out for several weeks now and it show's two things.
One, if you persist in telling the electorate something for long enough - regardless of the truth - they will eventually come to believe it.
Two, the Boris campaign will win unless Livingstone deals with the tax issue decisively because it's killing his campaign. Literally killing it.
It doesn't matter that the circumstances may be unfair. It doesn't matter that Livingstone is in effect revealing the tax affairs of his wife as well as his own and that Boris Johnson isn't. And just for the slow witted out there Livingstone employs his wife through the company he owns. So this is how is works: he pays corporation tax on the earnings of the company, she pays income tax on the wage she receives as an employee of that company and he pays income tax on anything else he receives that doesn't get filtered through the company.
All Clear? No? I'm nor entirely surprised. And therein lies the problem.
Livingstone's tax affairs are complicated. Not hugely complicated and from almost everything I have seen it doesn't look as if he has broken any laws or underpaid tax or tried to do anything dodgy. But when you got out there banker bashing and you earn quite a large sum of money yourself and then have complicated tax arrangements, your opponents only need make the slightest suggestion that you're hiding something before you find yourself mired in controversy for weeks on end.
The only thing that matters in this situation is perception. Reality doesn't come into it. In the case of Livingstone's tax affairs the perception among the electorate is now one of dishonesty and of double dealing.
Livingstone can talk all he likes about how he wants to help ordinary Londoners and cry during the launch of his campaign video but none of it will matter if he is already perceived as dishonest.
And as if to pile on the misery Livingstone's camp today had to admit that the ordinary Londoners in their campaign film - the ones that made Livingstone cry just the other day - were in fact Labour supporting Londoners reading from a script. So now Livingstone looks dishonest when it comes to money and emotionally manipulative and dishonest when it comes to campaigning.
I have to say I thought it was a bad enough idea to have Ed Miliband by his side at the launch of the campaign film now I'm wondering if the crying wasn't actually Miliband's idea. It seemed out of character for Livingstone in the first place and much more like Miliband's touchy feely kind of politics that no one is really interested in and will, by the way, never get you elected mate.
Even worse for Labour both the Prime Minister and the Chancellor of the Exchequer have mischievously said they might publish details of their tax affairs. In reality they won't. In reality this was a very subtle piece of manipulation designed to keep the issue of tax in the public domain. It was effectively (and very effective as well) election campaigning. And it has made Labour look like a bunch of amateurs.
Let's also not forget that people know that Boris Johnson is a very wealthy man. They knew it four years ago. They still voted for him. So there is little damage, if any, that Livingstone's camp can do to Johnson when it comes to his financial affairs. And unlike Livingstone, Boris hasn't gone around bashing the bankers; rather he's talked up the importance of the City as a major economic centre not just in the UK by the world. Poor people know whose side he is on and it isn't theirs but with Ken Livingstone they don't know what to believe anymore.
This was always going to be a pretty lousy election campaign fought as it is mid-term of a coalition government that despite numerous gaffes, riots across city centres all over the country last year and the biggest cuts to public spending in decades still probably has a better chance of securing a Conservative majority government next time round than a Labour one.
What irks me more than anything in some respects is that this is an election of who could care less. The main parties have provided us with the same candidates as four years ago, the issues haven't changed all that much and no-one really has much of anything new to say. The best the two main candidates can do is sling mud at the other's record in office.
Livingstone's policies are admittedly more detailed than Johnson's but no one is going to really vote for Johnson based on his policies. He's gotten by the last four years on a policy of what can best be described as (largely) benign neglect. Those people that will vote for him will do so for one of three reasons: 1) They still haven't grown up and think it will be funny to keep the posh duffer in for another four years despite many of us thinking the joke has worn a bit on the thin side. 2) They naturally vote Tory and live in the outer boroughs where they have trees and grass so don't really care all that much about what happens to the rest of London. 3) They're angry as hell over Ken Livingstone's tax affairs even if they don't fully understand them - which most won't.
As for Livingstone he touched a very raw nerve early on in the campaign with his promise to cut tube and bus fares but much of the rest of his campaign is about restoring something that has been cut in an era when people are asking, quite rightly, where the money will come from. Even if he has got his maths right, two years of being told there isn't any money will leave most people thinking that Livingstone won't be able to deliver on his election promises.
As much as Boris versus Ken might a piece of political pantomime it will very likely stop being entertaining long before polling day. Both camps should be far more concerned about voter apathy than by trying to get one over their opponent.
Right now Boris probably has the upper hand. And he will do until Ken can land a decisive blow of his own or owns up over his taxes. Of course come May 3rd there's also a good chance none of us will give a damn.
Follow Matthew West on Twitter: www.twitter.com/http://twitter.