"Whenever a candidate for nomination or election to an office is disqualified after 5:00 p.m. on the sixth Tuesday prior to a primary election, general election or special election to fill a vacancy, his name shall be printed on the primary, general or special election ballot, as the case may be. The election and canvass shall proceed, and, if a sufficient number of votes are cast for the disqualified candidate to entitle him to nomination or election had the candidate not become disqualified, a vacancy shall exist on the general election ballot or in the office to be filled in the manner provided by law."
Unless Akin resigns by 5 p.m. on September 25th then his name stays on the ballot. And if withdraws after that and he still wins the election then the seat is declared vacant and the Democrat governor fills it.
Thank you for that.
Linked for others to read:
http://www.sos.mo.gov/elections/laws/ch_115_pgs_3-152.pdf#p72
Section 115.359. Withdrawal of candidacy, deadline for, how made.