The 2006 MN 1st Congressional Election, a contest between six term Incumbent Gil Gutknecht and Public School teacher Tim Walz resulted in a strong upset for Walz in a district that at the time, had sent a republican for 100 out of the prior 114 years.
Entering politics after being harrased by the campaign for trying to attend a Bush 2004 campaign event, he took on the beleived to be safe incumbent, running a race that Republicans did not begin to see as a threat until October.
The reason they began to take the threat seriously? Walz's fundraising had kept pace with Gutknecht's despite the former being a first time candidate, and the latter an entrenched incumbent.
Herein, Walz and the DCCC attacked Gutknecht for opposing an increase in millitary benefits whilsed voting to increase his own congressional pay—whilst highlighting Walz's own support for gun rights, and millitary experience
By contrast Gutknecht attacked Walz for being a "liberal"; attacking him on taxes, illegal immigration, enphasizing how Walz's support for abortion rights and same sex marriage placed him outside the district's mainstream.
However, Walz's history as a High School Football Coach and veteran significantly blunted these attacks, preventing them fron sticking as they gave him a "Aura of Authenticity".
In the end, the head start Walz got from the GOP's carelessness, the Year's overwhelming democratic lean, and authenticity won out, giving him a strong 5.6% victory over the 12 year incumbent.