Publisher John Elchert says the ad appeared Thursday in The Warren Times Observer. It read, "May Obama follow in the steps of Lincoln, Garfield, McKinley and Kennedy!" The four presidents were all assassinated.
Elchert tells The Associated Press that advertising staff didn't make the historical connection, but the paper removed the ad Friday and turned the information over to police.
Elchert says an agent from the Secret Service office in Erie is in town, investigating the person who placed the ad.
A note in Friday's paper says, "The Times Observer apologizes for the oversight."