Suppose the majority in both parties (the left and the right-wing) are anti-free-trade, while the minority is pro-free-trade. Also, the majority regards spending as the more important issue while the minority cares more about trade issues.

a) Why is it possible to obtain free-trade as equilibrium policy choices for both parties?

b) What happens when one party becomes anti-free-trade?

(an reference that you find can be used to answer this question)