I don't think the actual levels of public spending Labour is pledging are politically costly - if you're *that* bothered by public borrowing and deficits, you probably didn't vote Labour in 2017 and probably won't now.

I think the political danger is in taxation. 1/

Labour remains committed (correct me if I'm wrong) to balancing day-to-day spending over five years. That excludes their mammoth capital investment programme. But it includes spending increases on the NHS, 'National Education Service' etc.

Those books will need balancing.
2/

That suggests tax rises. But Labour previously pledged to protect earners under £80k from income tax rises, and is likely to stick to that.

In 2017 Lab went big on income tax rises above £80k, corporation tax rises, and some low hanging fruit reversing Tory tax cuts (eg IHT) 3/

The costings weren't accurate but they weren't totally fantastical either.

But now there'll be extra pledges - on welfare, NHS, education, social care. Those need funding. How? 4/

One route is to simply factor in the benefits of higher spending - e.g. higher spending on care delivers savings for the NHS. This is logical but also risky (the Tories' SEND reforms were meant to be self-financing on this basis... HA!).

There might be some of this 5/

The other route is more transformational tax reform. And this is where the risks are. A floated Land Value Tax in 2017 nearly sunk their campaign. This has now been pared back to commercial property - but what effect will that have on local govt landlords? Has this been asked? 6/

What else might they go for? A lifetime gift tax to replace IHT is the sort of think tank policy that is logical but liable to anger voters. Equalising dividends tax with income tax makes a *lot* of sense but could hit the self-employed. 7/

We'll see what's in the manifesto, but look out for big tax reforms - proposals that make sense in think tank reports but don't translate well to an election campaign drenched with facebook ads.

It only takes one line in a manifesto to bring down a campaign /end

PS - I don't know how much it will matter whether the IFS and others say Lab's figures add up or not. Voters don't pay that much attention to the details - but if ppl think it's all unaffordable, they'll doubt your ability to deliver, reducing the electoral benefit of the pledges