Answer:
The collective dilemma for Democrats that this rule solve is a coordination problem .
Step-by-step explanation:
A coordination problem usually occur when individual in a group is left to decide on what to do based on their individual preferences without amortizing it with the choice of the entire group.
In the question, if each member of the Democrats is left to go and vote with a primary election, it possible that the Democrats if there is an even division of votes as result differing preferences for a particular Democrat to vote for.
Holding a primary election before the general election will make coordination easier as regards which candidate has been chosen to be voted in the general election. With this, it certain that at one the Democrats will be elected.
Therefore, the collective dilemma for Democrats that this rule solve is a coordination problem .