Click here to watch "Words."

Sticks and stones may break your bones, but words... can get you in a pretty big mess too. Presumptive Republican presidential nominee John McCain is up with a new Web ad today that attacks Democratic rival Barack Obama for his decision to opt out of the public finance system. The ad, called "Words," uses Obama's against him in an attempt to show that the Illinois senator flip-flopped on his position supporting the system.

The spot highlights various speeches and interviews Obama has given, including those where he pledged to work with the Arizona senator, as well as the video message he sent out informing supporters of his decision to forgo public financing. The ad repeats a clip of Obama saying "don't tell me words don't matter" while displaying various media reports chastising him for his change in positions.

Even though the two raised roughly even amounts of money in May, Obama has continually surpassed McCain in his fundraising efforts, which could help explain some of his reasoning for opting out. With his campaign raising a record-breaking amount nearing $300 million so far -- far more than the meager $84 million specified in the public finance system -- clearly Obama doesn't need the taxpayer help.