Democrats had a lot of candidates that people were rooting for and that appeared strong, but not all of them won. Some tried again in 2008 and succeeded while others failed once more. There were longshots in Bush districts that had all the buzz on sites like Swing State Project (which became part of DailyKos).
Here is the list of the major challengers and candidates for open seats with their districts and their percentage of votes. The ones with asterisks next to them (*) won their races.
Ellen Simon (AZ 1, 43.4%)
John Thrasher (AZ 2, 38.9%)
Harry Mitchell (AZ 5, 50.4%)*
Gabrielle Giffords (AZ 8, 54.3%)*
Charles Brown (CA 4, 45.4%)
Jerry McNerney (CA 11, 53.2%)*
Cynthia Matthews (CA 26, 37.9%)
Francine Busby (CA 50, 43.5%)
Angie Paccione (CO 4, 43.1%)
Jay Fawcett (CO 5, 40.4%)
Ed Perlmutter (CO 5, 54.9%)*
Joe Courtney (CT 2, 50.0%)*
Diane Farrell (CT 4, 47.6%)
Chris Murphy (CT 5, 56.5%)*
Charlie Stuart (FL 8, 45.7%)
Phyllis Busansky (FL 9, 44.1%)
Tim Mahoney (FL 16, 49.5%)*
Ron Klein (FL 22, 50.9%)*
Larry Grant (ID 1, 44.8%)
Tammy Duckworth (IL 6, 48.6%)
Dan Seals (IL 10, 46.6%)
John Pavich (IL 11, 44.9%)
John Laesch (IL 14, 40.2%)
Joe Donnelly (IN 2, 54.0%)*
Brad Ellsworth (IN 8, 61.0%)*
Baron Hill (IN 9, 50.0%)*
Bruce Braley (IA 1, 55.0%)*
Dave Loebsack (IA 2, 51.4%)*
Nancy Boyda (KS 2, 50.6%)*
John Yarmuth (KY 3, 50.6%)*
Ken Lucas (KY 4, 43.4%)
Sharon Renier (MI 7, 46.0%)
Nancy Skinner (MI 9, 46.2%)
Tim Walz (MN 1, 52.7%)*
Coleen Rowley (MN 2, 40.0%)
Patty Wetterling (MN 6, 42.1%)
Jim Esch (NE 2, 45.3%)
Scott Kleeb (NE 3, 45.0%)
Jill Derby (NV 2, 44.9%)
Tessa Hafen (NV 3, 46.6%)
Carol Shea-Porter (NH 1, 51.3%)*
Paul Hodes (NH 2, 52.7%)*
Rich Sexton (NJ 3, 41.0%)
Paul Aronsohn (NJ 5, 43.8%)
Linda Stender (NJ 7, 47.9%)
Patricia Madrid (NM 1, 49.8%)
David Mejias (NY 3, 44.0%)
Steve Harrison (NY 13, 43.2%)
John Hall (NY 19, 51.2%)*
Kirsten Gillibrand (NY 20, 53.1%)*
Mike Arcuri (NY 24, 53.9%)*
Dan Maffei (NY 25, 49.2%)
Jack Davis (NY 26, 48.0%)
Eric Massa (NY 29, 48.5%)
Larry Kissell (NC 8, 49.9%)
Heath Shuler (NC 11, 53.8%)*
John Cranley (OH 1, 47.7%)
Victoria Wulsin (OH 2, 49.4%)
Robin Weirauch (OH 5, 43.1%)
Mary Jo Kilroy (OH 15, 49.7%)
Zack Space (OH 18, 62.1%)*
Jason Altmire (PA 4, 51.9%)*
Lois Murphy (PA 6, 49.3%)
Joe Sestak (PA 7, 56.4%)*
Patrick Murphy (PA 8, 50.3%)*
Chris Carney (PA 10, 52.9%)*
Lois Herr (PA 16, 39.5%)
Nick Lampson (TX 22, 51.8%)*
Ciro Rodriguez (TX 23, 54.3%)*
Phil Kellam (VA 2, 48.5%)
Al Weed (VA 5, 39.9%)
Judy Feder (VA 10, 41.0%)
Andrew Hurst (VA 11, 43.6%)
Peter Goldmark (WA 5, 43.6%)
Darcy Burner (WA 8, 48.5%)
Mike Callaghan (WV 2, 42.8%)
Steve Kagen (WI 8, 51.1%)*
Gary Trauner (WY, 47.8%)
I keep in mind for 2018 that a lot of candidates will wind up losing in the end, even if they come very close. A lot of the 2006 wins had something particular to do with the district. For example, in PA 10 the incumbent had beat his mistress and so a Democrat won. There was the Mark Foley scandal in FL 16, the weak Democrat barely won (he lost two years later). Jason Altmire's victory over Melissa Hart was one of the night's big surprises. Dan Seals was the Brad Schneider of 2006 and he was up against Mark Kirk, a moderate Republican incumbent. His loss was a surprise since this was exactly the kind of district Democrats needed to win. One name from here is Tammy Duckworth who eventually did win a seat in 2012 and then of course in 2016 she beat Mark Kirk. She was a very strong candidate expected to beat Peter Roskam, who in 2018 is fighting to survive.
A few other memories:
In NM 2, the D candidate Patricia Madrid had an embarrassing moment in a debate which was used in an ad. She lost to Heather Wilson, but this seat was easily picked up by the Democrats in 2008 with Martin Heinrich (now Senator).
In WY, the incumbent was Barbara Cubin, who considering the very Republican lean of the state, did terribly. She almost lost to Gary Trauner.
The "Beto" of 2006 was definitely Scott Kleeb - Scott looked like he belonged on the cover of a romance novel and he had lots of swooning, but he was unable to win the open seat in NE 3. He was featured in an article from 2006 that talked about the hunky Democrats of that year.
https://www.youtube.com/watch?v=SqxEq5IVoVgIn the Senate races, Jon Tester and Claire McCaskill were both running against R incumbents and their races were very close and it wasn't certain if the Democrats even could win the Senate that year because of their races (along with the one in Virginia with Jim Webb). They are on the ballot again in 2018 and once again their races are tossups. I remember the Senate being considered out of reach for the Democrats by many pundits because they would have had to win 6 seats to take control and that was not easy - but they managed to win exactly 6. (Rhode Island, Ohio, and Pennsylvania were big victories but they still needed MO, MT, and VA.) There was also the Senate race in Tennessee where there was an ad that suggested that Harold Ford, Jr had sex with a white woman - that same exact seat is also open this year where the Democrat has a chance of winning.
