Nominations by the U.S. President
The Library of Congress created this resource which enables you to search for nominations by U.S. Presidents starting in 1981. There information about the nomination process, the records and related nomination resources at About Nominations of the U.S. Congress.
Unfortunately I did not find a link to bulk data for presidential nominations nor an API for the search engine behind this webpage.
I say that because matching up nominees and/or their sponsors with campaign contributions would help get a price range on becoming the ambassador to Uraguay, etc.
I wrote to Ask a Law Librarian to check on the status of bulk data and/or an API. Will amend this post when I get a response.
Oh, there will be a response. For all the ills and failures of the U.S. government, which are legion, it is capable of assembling vast amounts of information and training people to perform research on it. Not in every case but if it falls within the purview of the Law Library of Congress, I am confident of a useful answer.