I heard Major Garrett say on Fox News...that it would have to be a "write in" candidate on the GOP side...to take Foley's place.
Kind of like in Tom Delay's case...it has to be write-in..which pretty much means it will be a dem...in both cases.
According to the statute, Foley can be replaced with a new GOP candidate, however, since the primary has already been certified Foley's name must stay on the ballot but all his votes goes to the new candidate.
Section 4(a) is the relevent part
http://www.leg.state.fl.us/statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=Ch0100/SEC111.HTM&Title=-%3E2006-%3ECh0100-%3ESection%20111#0100.111
The Pubbies can get the word out about the replacement for foley and then also poitn out the democrats never make their congressmen caught up in scandal resign, case in point barney frank.