The Club for Growth is upping it investment in Conservative Party speciale election candidate Doug Hoffman, with another $300,000 ad buy beginning tomorrow.

The latest ad, interstingly, is mostly positive. After briefly labeling GOP nominee Dede Scozzafava and Democrat Bill Owens "liberals" at the beginning of the ad, it talks exclusively about Hoffman's bio and his credentials.

The Club has already spent more than $300,000 on the race, so this brings its investment to more than $600,000 total. 

By comparison, the NRCC has spent $567,000 on Scozzafava's behalf, and the DCCC has spent $387,000 on Owens's behalf.

Also in recent days, SEIU has gone up with a $100,000 radio ad buy for Owens -- its first investment in the race.