The scandal broke on September 28. Here are the generic poll numbers for the preceding month:
BattlegroundBattleground 9/24 - 9/27 1000 LV 41 49 Democrats +8
FOX NewsFOX News 9/26 - 9/27 900 LV 38 49 Democrats +11
Hotline/FDHotline/FD 9/24 - 9/26 423 LV 33 46 Democrats +13
ZogbyZogby 9/22 - 9/25 1000 LV 33 42 Democrats +9
CNNCNN 9/22 - 9/24 573 LV 42 55 Democrats +13
CBS News/NY TimesCBS News/NY Times 9/15 - 9/19 1007 RV 35 50 Democrats +15
LA Times/BloombergLA Times/Bloomberg 9/16 - 9/19 1347 RV 39 49 Democrats +10
USA Today/GallupUSA Today/Gallup 9/15 - 9/17 1003 A 48 48 Tie
AP-IpsosAP-Ipsos 9/11 - 9/13 1501 A 39 53 Democrats +14
FOX NewsFOX News 9/12 - 9/13 900 LV 38 41 Democrats +3
NBC/WSJNBC/WSJ 9/8 - 9/11 1009 RV 39 48 Democrats +9
Pew ResearchPew Research 9/6 - 9/10 1191 RV 39 50 Democrats +11
GallupGallup 9/7 - 9/10 925 RV 41 53 Democrats +12
ABC NewsABC News 9/5 - 9/7 1003 A 42 50 Democrats +8
CNNCNN 8/30 - 9/2 1004 A 43 53 Democrats +10
FOX NewsFOX News 8/29 - 8/30 900 RV 32 48 Democrats +16
http://www.realclearpolitics.com/epolls/other/2006_generic_congressional_vote-2174.html#polls
Fourteen of the sixteen polls gave the Democrats at least an eight point lead. I don't deny that the Foley scandal further damaged the GOP, but the overwhelming majority of the pre-Foley polls did *not* show a virtual tie.