DWC has since deleted that claim. That Sioux Falls paper ha since deleted the validity of that claim:
Republican and conservative groups spent about $2 million to help Noem win, most of it in the form of ads criticizing Herseth Sandlin. Democratic and liberal groups spent close to $600,000, most of it in ads against Noem, according to Federal Election Commission reports analyzed by the Sunlight Foundation, a nonpartisan Washington watchdog think tank.
Herseth Sandlin said the influx of outside money definitely contributed to her defeat.
"We were outspent pretty heavily," she said [Ledyard King, "Outside Groups Backed Noem 3–1," that Sioux Falls paper, 2010.12.05].
Those outside groups do love ladies on horsies. And contrary to the spin offered by the Noem campaign and its fawning conservative blogs, those outside groups were instrumental in helping the less-qualified Noem eke out a slim plurality of the vote.