I've read just about every thread in this forum and have not found an answer to this--#2 specifically for the reason you mentioned. If you hold out your highest contribution card, you might score some extra party membership.
If I play the official "short variant" of the Valley Games version, I will have 5 elections and each player will have 4 Contribution cards. So do we:
1) Only play Contribution cards after rounds 1-3, because there is no reason to get money after round 4 because there are no further actions to be paid for. In this case, each player has a choice between 2 contribution cards for that 3rd-round Contribution phase, and each player will also end the game with 1 unplayed contribution card.
2) Play contribution cards after round 4 as well. Obviously each person will not accept the $$ from this final contribution, and instead choose to increase National party membership. But someone may get the bonus dice rolls if they play a higher-value contribution card than anyone else in this final round.
I'm leaning toward 1 but am interested if there is either a definitive ruling or opinion. Looking forward to our group's first play of this tonight.