I'll fess up here. I read the Mail most days. But I also read Holy Moly and Popbitch, and for similar reasons. I don't regard any of them as politically serious.
In fact, there's decent evidence that the political importance of the dead trees was over-rated, even before their circulation began to fall. Here's one US study (pdf) by Jesse Shapiro and colleagues:
We find no evidence that partisan newspapers affect party vote shares, with confidence intervals that rule out even moderate-sized effects. We find no clear evidence that newspapers systematically help or hurt incumbents.
This is consistent with John Curtice's assessment (pdf) of the 1997 election:
Relative to the often highly evocative and strident manner in which the British press often conducts itself, its partisan impact is a small one.
Since then, it's highly likely - given their falling sales - that newspapers' influence has declined further. In the last general election, there was no relationship between the papers' political positions and aggregate votes.
Sure, there is some countervailing evidence. Fox News does seem to have influenced American voters; a neat experiment suggests papers can affect voting; and there's evidence that local papers can encourage turnout and hence improve the vigour of local democracy.
Of course, journalists think that newspapers matter enormously, but then sausage-makers think that sausages matter a lot. We should take neither at their word.
I fear that lefties who fret about the Mail's antics are actually playing into its hands. Like a has-been popstar craving attention, the papers are resorting to ever-more desperate efforts to attract eyeballs. Linkbait is now a business model, and your outrage is their profits.
Let's be clear. The newspaper business is a relatively minor one - the average household spends less each week on papers than it does on fish - which doesn't deserve the attention we give it.