Suppose you’re an embarrassment to your political party.  In many countries, your party can formally expel you.  This serves three functions. 

First, damage control.  The fact that your party expelled the embarrassment mitigates your guilt-by-association. 

Second, prevention.  After you’re expelled, your future behavior will bring little further shame to your former associates. 

Third, deterrence.  The fact that parties can expel embarrassments gives members an incentive to watch their mouths and control their behavior.

As far as I can tell, however, neither the Democrats nor the Republicans have the power to expel members.  Which raises some questions.

1. Is it strictly true that Democrats and Republicans cannot expel party members?  Or are there procedures they never (or almost never) use?

2. If expulsion were an option, who would the Democrats expel?  Who would the Republicans expel?

3. How would this change the style of American politics?

4. Would it have any effect on actual policy?

Please show your work.