The always thought-provoking Tim Worstall asks this question, to which we all know the answer:

Absolutely every commentator even vaguely left of centre says that
the fiscal contraction (ie, the combination of spending cuts and tax
rises) is going to devastate the economy. We’re going to get a double
dip recession, unemployment will go over 4 million etc.

Let us imagine that this doesn’t happen: will we then have put to
bed the idea that only government spending can get us out of such
recessions?

Or if, in two or three years time, this hasn’t happened, will they just walk away whistling, hoping no one will have noticed?