The 59-year-old Deputy Leader has reportedly received a number of nominations for the award, since her performances standing in for Prime Minister Gollum Brown at PM's Questions in recent weeks.
A spokesman for the National Equine Society confirmed that Mzz Harperson was now the front-runner for 'Horses' Rear of the Year', beating strong challenges from champion hurdler Celestial Halo and Grand National winner Mon Mome.
NES Spokesman Jock. E. Rider said, "Harperson is a surprise leader in the standings. The truth is, she's not got the best-looking of rumps, she lacks muscle tone and her tail needs work - but in terms of overall performance, she goes into the lead for the multi-purpose nature of her backside. After all, she's the only contender who talks out of it."
Mr Rider added, "we expect a significant number of further votes for this mare as time goes on, due to the sheer number of people who would dearly love to drown her in Bechers Brook."
However, Mr Rider also confirmed that Mzz Harperson has not been nominated for Horses' Face Of the Year, with the award going to Baroness Ashton - the first time in a decade the accolade has not been presented to Margaret Beckett.