Why would a man whose entire political career is based on being presentable be so apprehensive about a TV debate?
David Cameron's reticence over the election debates - which will, despite everything, almost certainly take place next year - is partly explained by an observation in a Lords report this morning.
Peers found TV debates were "helping to energise and engage the public in the electoral process, with the most striking impact on the young and relatively disengaged".
TV debates bring in people who are usually disconnected from politics. That is one of the reasons they proved so anarchic and unpredictable in 2010. No-one saw Cleggmania coming. Even as the debate was unfolding I found the way he kept on staring down the camera intrusive, rather than charismatic or egalitarian. Once it was over, polls were doing things which politicians and political journalists had not predicted. They then failed to predict that Lib Dem popularity would pretty much all dissipate by polling day.
The reason for the chaotic effect of the debates seems to be that they were engaging people who typically do not engage in politics. The Westminster bubble is simply unaccustomed to young, disconnected people suddenly taking an interest in it.
For Cameron that anarchic potential poses a threat, because although he is slightly behind in the polls and faces an in-built Labour advantage in the electoral system, he has several advantages which he can rely on.
He enjoys a sympathetic press who will attack Ed Miliband with an unmatched ferocity once the election campaign begins, he leads on 'valence' qualities like strong leadership and 'being up to the job', and he will be expecting the standard poll consolidation for whoever is in government in the days immediately before the vote.
The last thing a leader in that position wants is for a wildcard element to be thrown into the campaign at the last minute. That's one of the reasons why, if they are forced to join the debates, the Tories will want them as early in the campaign as possible, so there is plenty of time to douse any fires which emerge before people go to the polls.
Of course, Cameron's hesitancy over the debates belies his crisis of confidence in his own professed strengths. If Cameron's team were so sure of his tough, prime ministerial qualities you'd have thought they'd welcome the chance to show them off in a debate.
The presence of Nigel Farage is a problem of course. But the Tories' concerns are also a reflection of the fact Cameron really isn't very good at this format. Even in his Cameron Direct events he comes across, at best, as a distracted patrician and at worst as an arrogant snob having to mix with the hoi polloi.
Miliband, on the other hand, is actually rather good at these things. He's likeable, mostly human and sounds reasonable. One of the reasons his team are so keen on the debates is that it gives him a chance to speak to the public over the heads of a hostile press.
Cameron would rather avoid that, much as he'd rather avoid the involvement of young and disconnected voters.
It's the fact the debates reach disconnected voters which makes Downing Street wary of them.