So how exactly is it that Jon Corzine has been catching up with Chris Christie in the New Jersey gubernatorial race? A lot of it has had to with women voters -- and mammograms.

Over the last several weeks, Corzine has been relentlessly hammering Christie over his advocacy of legalizing mandate-free insurance policies -- that is, not subject to state requirements that they cover certain procedures, which under New Jersey law include mammograms, autism screenings and other preventive care.

James Wolcott notes that this ad in particular has been given heavy rotation, warning women voters, "But if Chris Christie was governor insurance companies could drop mammogram coverage."

A recent Monmouth poll found that this was making for an effective wedge issue among independent women voters: "While these voters had been giving their soft support to Christie based on discontent with the Corzine economic record, they appear to have beaten a hasty retreat when threats to their health care access were raised."

Christie has called the ad "deceitful" and "awful," citing his own mother's battle with breast cancer. At the recent debate, he said: "So let's make it really clear. I would not have a plan that would ever prevent any women who needed a mammogram to get one. The governor knows it, and this is just another example of his shameful campaign."

But he can't seem to be able to dodge the attack, and has even had to modify his tactics. As the Corzine campaign pointed out, Christie's campaign recently edited their Web site's issue page on health insurance, eliminating the term "mandate-free" and presenting such policies as an alternative for consumers.

This issue seems to be working for Corzine, so don't expect him to give it up any time soon.