They don't of course ... not often, but the tension is real, and for a politician, being good in a debate is a real skill. To be honest I think it's a gift. You either have it or you don't.
David Cunliffe this time three years ago was beside himself when I walked into his green room.
You could literally cut the air with something sharp.
He looked like the hunted, he put on that front you do when you know none of this is fun and things aren't going your way but you'd rather die than admit it.
Trouble with that is anyone with any experience in such matters can sniff it a mile away.
He also had too many people in his ear. The room was full of hangers-on. In the other green room John Key had turned up by himself with only his security detail. The contrast could not have been greater.
Jacinda Ardern asked me the other day whether I enjoy the debates. I said I loved them.
It is a privilege, in a broadcasting sense, but they are hard work.
Just making it happen, making it flow, the timings, the balance, the commercials, the technical aspects are many and varied and while you're doing all of that you're listening to answers and working out what the next question is.
I told her about Cunliffe and the pointlessness of working yourself into a frenzy.
Her distinct advantage is she comes in with a sail full of wind. She has the momentum. She must feel good about how the past couple of weeks have gone. That gives you confidence.
Where she has trouble is in the experience stakes.
She faces a bloke who has done it all.
He knows the country, he knows the economy, he has a very positive story to debate.
But he also has two distinct issues that could trip him up.
Firstly his personality. I hope he finds it because on the bad days it's missing in action.
He needs to come to life.
Say what you want about policy and records, personality counts. Jacinda Ardern is indisputable proof of it.
He also has to watch how he deals with his opponent.
He can't look or sound condescending, he can't use his experience to lord it over her. Any hint that he's being sexist or misogynist and he will be jumped on by the ever-expanding group of the permanently aggrieved who start each day looking for a scrap.
Bill English v Andrew Little would have looked and felt completely different to what you will watch tonight.
But ultimately what makes these events so gripping is not what is said, but what isn't.
That is the beauty of TV and a cauldron type atmosphere like a debate.
The face, the expression, the pauses, the looks, you can see what is not being said.
And that applies both to those who perform well and not so well.
For Ardern a good night is a chance to cement her credentials as a genuine contender for the top job.
For English it's the chance to stop the Labour momentum and get his party back on the front foot, having had the air sucked out of the room by the Labour spill.
For both, the stakes are huge.
