Does it stack?

Priority Contract and Black Throne, The
Can you collect 4 pool or does the timing not work?

Black Throne, The

[1 Pool]

Master: unique location.
Tap during a referendum to gain 2 votes. Tap when a minion with a contract leaves the ready region (only usable if an Assamite you control had been chosen for that contract) to gain 1 pool.

Priority Contract
Master

Unique contract. Trifle.
Put this card on a minion controlled by your prey and choose a ready Assamite you control. The chosen Assamite can enter combat with this minion as a +1 stealth action. If this minion would leave the ready region, you can burn this card to gain 3 pool.

Yes it works