I suspect that radical honesty - with clear, consistent communication - about the consequences of not broadening the tax base would not be liked but would be accepted.

The moment for that was July 2024 - preferably having not put impossible red lines in the manifesto.

Now is the next best time.

Also there is nothing remotely honest about pledging not to raise income tax, and then freezing the threshold so that people pay more income tax.

Stealth tax rises are probably more damaging than openly and honest arguing for clear rises.