There was a fascinating piece on the "Today" programme this morning (scroll to 1:20:35). Listen to these voters try and identify party policies (they mostly fail), and then explain why it doesn't matter anyway. They may or may not be a representative sample, but these ordinary voters are classic examples of the principle of voting with the gut rather than the mind. They are happy that they don't really understand any policies, it doesn't matter what detail parties promise as "they all promise the same and never deliver". The personality of the leader is the most important thing.
Parties spend a lot of time developing their manifestos. Voters spend a lot of time ignoring them and then claiming the promises don't amount to a hill of beans anyway. Win the battle of perception and you've pretty well clinched the election. That's Lynton Crosby's key understanding, and Theresa May - neither particularly strong or particularly stable as it happens - is his most obedient pupil. Of course she's winning. Policies have nothing to do with it.
One friend who has been canvassing for the Lib Dems reported a voter telling him that it was important to vote for Theresa May as she needed all our support to negotiate for Brexit. That's nonsense and it doesn't actually mean anything. But it is the simple mantra put out regularly by May and co, and a voter who doesn't spend much time thinking about politics has swallowed it whole.
Want to be depressed about human nature? Want to understand Thomas Hobbes a bit more? Follow an election!