“one percent, the recount threshold in Missouri.”
http://www.kansascity.com/news/local/news-columns-blogs/the-buzz/article26740141.html
as of 2015
It appears that a recount can be requested if the difference is less than 1%
115.601. Recount authorized when less than one percent difference in vote—recount,
defined.—1. Any contestant in a primary or other election contest who was defeated by less than
one percent of the votes cast for the office and any contestant who received the second highest
number of votes cast for that office if two or more are to be elected and who was defeated by
less than one percent of the votes cast, or any person whose position on a question was defeated
by less than one percent of the votes cast on the question, shall have the right to a recount of the
votes cast for the office or on the question.
http://www.sos.mo.gov/cmsimages/electionGoVoteMissouri/2015ElectionLaws.pdf
I’m not sure if recounts apply to political party primaries.