Evan Tracey at the Ad Age "Campaign Trail" blog has some fascinating numbers:
Every day now there are an average of 880 political and issue ads directly or indirectly related to the 2008 presidential race airing on TV. The majority of these are in and around Iowa (354 a day) and New Hampshire (324 a day). Added to the TV ads there are radio ads, direct mail, robot-calls and door knocking all related to the presidential campaigns. So what does this mean? It's time for the negative ads to hit the air.
The 2008 presidential primary race is proving to be highly volatile. The bout of negative campaigning for which we are due will only add to the volatility. Attacks work in strange ways - they may hurt a candidate among undecided voters, but they could also harden support for a candidate among those already committed to him, or backfire altogether and hurt the attacker. Though with all the attacks and counterattacks that probably will soon hit the airwaves, it's equally likely that people won't know whom to blame for which attacks, and will reward the candidate who seems generally to stay above the fray.