Incumbents who won reelection after running behind in most late polls

[Mr.Phips]

On the Senate side, I can think of:

2010:  Michael Bennet(D, CO), Harry Ried(D, NV)
2004:  Lisa Murkowski(R, AK)
1996:  Bob Smith(R, NH)
1992:  Al D'Amato(R, NY)
1990:  Jesse Helms(R, NC)
1978:  Charles Percy(R, IL)
1974:  Bob Dole(R, KS)

On the House side:

2012:  Tim Matheson(D, UT-04), John Tierney(D, MA-06), Jim Beneshiek(R, MI-01)
2008:  Don Young(R, AK-AL), Paul Kanjorski(D, PA-11)
2006:  Heather Wilson(R, NM-01), Chris Shays(R, CT-04), Jim Gerlach(R, PA-06), Deb Price(R, OH-15).
1992:  Don Young(R, AK-AL), Jim Lightfoot(R, IA-03), Ron Coleman(D, TX-15)
1990:  Craig James(R, FL-04)
1982:  Ike Andrews(D, NC-04)
1978:  Abner Mikva(D, IL-10)

[Snowstalker Mk. II]

Heitkamp in 2012, Kyl in 2006.

[Miles]

2010 House
Bishop (GA)
Costa (CA)
Murphy (CT)
McNerney (CA)

[publicunofficial]

Heitkamp in 2012, Kyl in 2006.

Heitkamp doesn't apply, as she didn't win RE-election.

[Vosem]

Heitkamp in 2012, Kyl in 2006.

Didn't Kyl merely win by a greater-than-expected margin? I thought he was favored prior to the election, however.

[Mr.Phips]

Heitkamp in 2012, Kyl in 2006.

Didn't Kyl merely win by a greater-than-expected margin? I thought he was favored prior to the election, however.

Yeah, there wasnt a single poll that had Kyl ahead by less than five and that was a Democratic poll. 

[Zioneer]

Jim Matheson, not Tim. Also, the poll that had him running behind was shown to be faulty, so there's that.