Effects of Trade Policies and Tariffs

Some politicians, labor unions, and special interest groups argue that US trade deficits are harmful to the economy and nations that run large trade surpluses with the US are benefiting from unfair trade practices and agreements. These parties support increasing tariffs on imports, elimination, or re-writing of trade agreements. 

Write a minimum of 175 words:

Discuss what credible economists say about the effects that tariffs, changing trade agreements, and/or manipulating exchange rates will have on the total US trade balance.

Do you agree with their assertions? Why or why not? 

Please cite resources or references.