Arthur_itus asked a question in the first post that I don't think was ever answered. Why mid-term elections? The over-simplified answer-
Early on, the originators and emenders of the Constitution believed that, to avoid upheavel, not all members of Congress should be elected all at once.
Senators serve a six-year term. Every two-years, one-third of the senators are elected. This is supposed to ensure some continuity.

Representatives serve a two-year term. All of them are up for election every two-years, thus for them, the term 'mid-term' really doesn't have meaning- it is the time for all of them to be elected or rejected.

The changing winds of politics almost always seem to blow more strongly in the period about two-years after a presidential election, thus the Congressional elections reflect the attitude of the voters at that time. More often than not, the winds have blown against the President and the congressional members who support him.

Now posters can get back to throwing knives at each other-