What has been the most common reason for one-party losing control the national government

In the electoral history of  the US and other democratic countries, except for unusual circumstances or events, the economy is the main concern of voters. People are more concerned about having jobs, getting incomes to raise kids and keep families, having the possibility of buying a home, and so on. Normally, people are less worried about events in foreign countries.  

Explanation:

Dear Friend,

I wish you could see the amazing places I've visited in my time here. As you know, I landed in the busting port city of Osaka where my considerable travel boat was dwarfed by the impressive atakebune ships that streamed from the shipyards to the naval posts further out to sea. The Japanese are very organised, there is little that their vigilant customs officers miss upon entering, and this thorough spirit seems to permeate all sections of their law enforcement. I have been here for two months now and I believe I have yet to wash off the fishy aroma I picked up during my stay in the city, even though I have been away from it for a while now, and surrounded by the most beautiful mountain range with a rich variety of plants and animals, I do, however, have to be careful what I eat, as some of the local lords are very strict when it comes to what is theirs.

I hope to hear from you soon,

Your friend

Dear cousin,

Yesterday I witnessed a very interesting sight, two little boys were playing at samurai, this reminded me of our games as children, I remember our oaths of chivalry and honor. Their's are little different to our own, except maybe that they take honor more seriously than we did. The eldest boy was about 10 years old, and the youngest 7, sons of a local farmer, I heard later that they got a good talking to for forgetting their chores and aspiring for things outside their station. I am learning to read the language, and my friend has lent me some precious scrolls for this, as I read the moving poetry out loud, I am reminded of the song of the forest in the lowland, the birds seem to chirp their way through the words on the page, and bring to life the delicate illustration on the margins. I hope to read to you one of these poems some day.

Until then, give my regards to our aunt,

Your cousin.