The invention of the radio was important for politics because

The invention of radio was important for politics because their messages/propaganda was able to reach the bigger masses. 
The radio was a revolutionary invention, and the politics used it in its service to the maximum by using it as a medium through which they can place their messages, ideologies, propaganda, and than the same to reach the people all over the country.

A. democrat, republican, whig, other.(the democratic and republican parties are the main 2 american political parties, the whig party was popular among the early presidents, and the “other” option allows for outliers)