Methodology
https://www.pewresearch.org/short-reads/2013/10/03/the-2016-presidential-media-primary-is-off-to-a-fast-start/
The 15 newspapers included in this search were USA Today, The New York Times, Los Angeles Times, Daily News (New York), The New York Post, The Washington Post, Chicago Sun-Times, The Denver Post, Chicago Tribune, The Dallas Morning News, NewsDay, The Houston Chronicle, Tampa Bay Times, The Star-Ledger (Newark, NJ) and Star Tribune (Minneapolis, MN). Only stories that were included in the print edition of the newspapers, were searchable on the LexisNexis database and were 500 words or more were counted.
The Boolean search used to identify stories that mentioned the campaign was: BODY((democrat OR republican) AND (president AND 2016 w/25 campaign) OR (president AND 2016 w/25 election)). The Boolean search used to identify stories that referred to an individual as a potential candidate was: BODY(NAME AND 2016 AND (president w/25 candidate)).