If someone wanted to be a US Senator prior to the 17th amendment how would you go about doing that? Did people campaign against one another within the legislature? If people were simply appointed did anyone ever turn down that appointment?
The Constitution goes into this one in Article I, Section 3:
The Senate of the United States shall be composed of two Senators from each State, chosen by the Legislature thereof for six Years; and each Senator shall have one Vote.
Immediately after they shall be assembled in Consequence of the first Election, they shall be divided as equally as may be into three Classes. The Seats of the Senators of the first Class shall be vacated at the Expiration of the second Year, of the second Class at the Expiration of the fourth Year, and of the third Class at the Expiration of the sixth Year, so that one third may be chosen every second Year; and if Vacancies happen by Resignation, or otherwise, during the Recess of the Legislature of any State, the Executive thereof may make temporary Appointments until the next Meeting of the Legislature, which shall then fill such Vacancies.
Just to reiterate/explain that, 1/3 of senators would be up for re-election every 2 years (6 year terms) as today. They would be chosen by the Legislature (from each state), meaning the elected representatives in the Legislature chose them. So in a way, yes, there were campaigns within the Legislature for who to choose. Appointments were only made by the executive (ie. governor) when the spot became vacant.
You can find the Constitution at this site, and anything underlined/hyperlinked means it's been changed by an amendment. Clicking it will take you to the amendment, which you'll likely want to know about :).