That's a term that might broadly apply to an awful lot of what's going on in the US, but I'm talking about a very specific tactic.

A very simple and exaggerated-for-effect non-political example:

An acquaintance comes to you and demands $100. You refuse and make it clear you intend to give them nothing. They then pull a gun on you and repeat their demand for $100. You steel your resolve and continue to refuse. It goes back and forth like that for a while, but you won't budge, so finally they say, "Okay then - how about if we compromise and you give me $50 instead."

That's effectively what Tuberville, through Sinema, is attempting. And it's a somewhat common political tactic - enough so that I suspect it has a name.