What does it mean?

I’ve seen " if push comes to shove"- which I think it generally means, " if necessity comes". However, in this case, push has now come to shove seems to refer to more than " necessity has come. Could you explain what it means and also tell me if it is common usage or not.

I have not read the text in question, however “if push comes to shove” means, as you say, “if we really have to do something”. I do not know the origin of this expression.

Thank you for answering my question, Steve. "the push has now come to shove " was used in the context as follows:

the last ten years the municipal governments that now make up Toronto have been cutting and cutting and cutting a total of about $500-million out of a $6-billion budget, and at the same time had tax freezes. And push has now come to shove. There's some inflationary pressures, our workers after a decade have finally got a wage hike, and of course the provincial government here in Ontario has downloaded a number of responsibilities to the city that add up to about $250- million a year. So we have a shortfall.

As you say, “if push comes to shove” means, " if we really have to do something", then I guess " push has come to shove" in this case means, "And the worst has come and we have got to do something. "
But I’m not sure. Please tell me if I am wrong.

Yes, you are correct.