:::: After a bit of WP:GOOG it appears that Schulyer Colfax also resigned, during his third term as speaker, albeit that one might not "count" as a resignation since he only served one day of that third term, and was resigning because he was elected veep.  See the article about Theodore M. Pomeroy for the details of the resignation-event.  Ping , it is definitely the case that Boehner is not the third speaker to resign.  Depending on how one counts, Boehner is either the fourth, fifth, sixth, or seventh.  But definitely not the third, so please remove the buggy sentence.