California's Eighth Congressional District has a large majority of Democratic voters and is represented by Paul Cook. However, if the general election pitted Cook against a second Democrat and a Republican, the Republican candidate might win if the Democrats were evenly split. For this reason, the Democratic Party requires any Democrat wishing to challenge Cook to face him in a primary before the general election. What collective dilemma for Democrats does this rule solve?

A coordination problem

Explanation:

This can best be thought of as a coordination problem.

Democratic voters in this district likely would prefer either Democrat to win compared with the Republican.

However, voters may have different preferences for which Democrat they most prefer.

By having a primary election first, Democratic voters can coordinate on which candidate to vote for in the general election, thereby making sure that they at least will elect one of the Democrats.

The collective dilemma for Democrats that this rule solve is a coordination problem.

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.