Eh? They didn't/aren't using their stockpiles to anywhere near the extent the US has! There reserves are much bigger - they have about a years supply - yet they used less in absolute terms than the US!

What they did was aggressively reduce demand by accelerating the switch to EV's and firing up a few more coal powerstations.

In terms of influencing the midterms - I suspect China isn't anywhere near the front of the queue in hoping Trump get's a beating given the chaos he is causing.

Complaining about foreign interference is ironically straight from the Hillary playbook.