The Humane Society's political arm has accused Rep. Joe Knollenberg (R-Mich) of having one of the "worst records on animal cruelty in the country" in a new ad launched to stop his ninth-district reelection bid.

The group says Knollenberg voted against a slew of animal-protection measures that includes a ban on the slaughter of horses, $800,000 to improve enforcement of anti-animal-fighting laws, and a ban on the importation of polar bear heads and hides.

Knollenberg is locked in a tough reelection bid against Democrat Gary Peters. A recent poll conducted by Mitchell Resources, a GOP consulting firm, showed the race tied at 43 percent.