Do you prefer your potatoes mashed or roasted? Which are better, cats or dogs? Is it reasonable for your aunt’s next-door neighbours to play loud music after 11pm? If pressed, you will have a view about all of these things. (For me it’s roasted, dogs, and probably not but it’s all right every once in a while if they’re having a party or something.) But a view isn’t usually the same thing as a deep concern. Most people prefer dogs; this doesn’t mean that cat lovers feel like an oppressed minority. I expect we’re pretty evenly divided on the best way to prepare a potato; this doesn’t mean that the nation is at war. No one spent a single moment worrying about the vexed matter of your aunt’s eardrums until she asked them about it.

As it is with ordinary life, so it is with national affairs. Political scientists call this salience: the idea that, as well as what you think about something, it is worth asking whether you think about it. Basic as this political concept is, it’s dismaying to watch our leaders merrily ignore it in favour of a frothing attention to their personal red-button issues.

David Cameron ignored his own advice to stop “banging on about Europe” to call a referendum, despite the fact that only 1% of people cared about it when he came to power. Perhaps this is why Theresa May seems newly alive to the importance of focus: whatever she ends up doing in practice, her rhetorical attention to social justice has been ruthless. Now she will open the debate before today’s vote on Trident – which her party will breeze through in a spirit of complete unity – and, as ever, Labour appears hopelessly divided on something that most people don’t care about.

They don’t care whether Jeremy Corbyn is leader of the Labour party. (Unfortunately, that doesn’t mean they’re ever going to vote for him.) They no longer care about the invasion of Iraq, which remains a shibboleth for a huge segment of Labour activists, even though it began more than a decade ago and all of the key players have departed from the stage. And they certainly don’t care about the particulars of Trident. This is, nonetheless, the issue that Corbyn seems prepared to go to the stake for, telling the Guardian yesterday that he “will be voting against continuous at-sea deterrent, because it rules out any compliance with the nuclear non-proliferation treaty”. This is fine, but it is not a sentiment that is likely to cut through on the doorstep.

Meanwhile, the shadow foreign and defence secretaries – Emily Thornberry and Clive Lewis – plan to abstain, and the official party position is in support of a deterrent. This baffling battle is for ground that voters haven’t visited for decades; and the vote will go through regardless. It is, in other words, Corbynism to a T. And until the leader or his successor can set the terms of a discussion about something that voters might actually care about, they will find that voters don’t care about them, either.

The surveys on salience don’t ask voters which political parties matter to them. But if they did, they would find that Labour had dropped off the scale a long time ago.