Some debates are marked toxic from the start. Try the existence of our old chums fairness and balance in reporting Jeremy Corbyn, for instance. The Times clears its front page to announce that Jeremy’s “on course to win a bigger mandate” than he did first time round, according to YouGov. Perhaps that means the media campaign, real or perceived, against him isn’t working: or perhaps it shows the BBC and other supposed culprits aren’t hopelessly biased after all.

But stir in 170 or so dissident MPs and some equally decisive opinion polls pointing in a precisely different direction – down and out – and objective truth sinks into the mists, leaving only one vital difference behind.

Fairness and balance can be media mantras at general election time, or whenever they directly affect national decision-making. It’s not so certain, though, that they apply as tightly to the choices that are made within the closed circuit of internal political-party voting. The decisions there are for paid-up members, not Joe and Joanna Public. How does the fairness principle work with people who mostly made up their minds when they put £25 in an envelope?

In fact, in many ways the most contentious current election reporting doesn’t touch Labour at all. Last week, with only a flicker of media interest, Lisa Duffy, Bill Etheridge, Elizabeth Jones, Phillip Broughton and Diane James formally asked 39,000 Ukip members to choose one of them as successor to Nigel Farage.

Oh, Ukip! you say. Who wants day-by-day coverage there, profiles, constant polling, open debates, in-depth reportage plus the full three-ring circus treatment? Didn’t we see Nigel on the stump with Trump in Mississippi? Isn’t that fair and balanced enough to keep the BBC Trust in chocolate biscuits?

But consider … As a prescient Frank Field MP told the Times: “Who gets elected leader of the Labour party obviously matters in determining its future. But the centre of gravity is shifting. Already Labour’s future may depend less on who wins the contest between Jeremy Corbyn and Owen Smith than who is elected Ukip’s leader.”

Ukip scored 3,881,099 votes in the 2015 general election. More than the Lib Dems and SNP put together. Its current poll rating, even leaderless in the lee of Theresa, mostly hovers in the 14% region. Last June, at Brexit time, it was five or six points higher than that. Without Ukip, Remain would have won. Editorialists talked obsessively, post-referendum, about the disaffected white legions of the north and Midlands in revolt against London’s elite. Yet where is that newfound extra-metropolitan fascination when Ukip makes its own top choices?

The answer, of course, is that it’s convenient to forget. Only the Daily Express – mindful of Richard Desmond’s party donations – has made any consistent effort. The Telegraph and the Mail, like the Mirror, seem happy to push the competing quintet to the periphery. Of course there’s some coverage: the Guardian, like the Times, keeps an eye on things from time to time. But Frank Field’s centre of gravity hasn’t exactly shifted yet. No one bar the Express seems to acknowledge it has Ukip readers on board.

Who cares? Labour supporters and mainstream Tories don’t want nonentities to become entities by bringing them in from the periphery. BBC interviewers obviously fret when immigration interviews lurch out of control. Five is an unwieldy studio number. You can understand, and possibly applaud, all of this. Pragmatic convenience. But is it fair? Is it balanced? Do such things – issues of supposed principle – matter if … well, if it’s just Ukip?