This is a great example of the Appeal to Emotion, specifically an appeal to pity. Bilbray is leveraging the tragedy of his daughter's cancer to appeal to voters. He is not making any rational argument about why he would be superior to his opponent, Scott Peters. He is basically arguing, "My daughter has cancer. Vote for me." If we think a little more deeply about the ad is should be clear that this emotional appeal makes absolutely no sense. Are we supposed to believe that Bilbray's opponent Scott Peters won't make any efforts to fund cancer research? Are we supposed to believe that Bilbray has some special powers as a congressman that would make him more successful in curing cancer or funding cancer research? Is his mere presence in a lab looking over the shoulder of a researcher with a microscope supposed to somehow improve the speed and efficacy of that research? The exact mechanism here isn't very clear, but then it isn't supposed to be. Bilbray is hoping that our pity and sadness at his daughter's tragedy is sufficient to block a rational assessment of the ad.
I must also comment on Bilbray's boilerplate at the end when he says, "I approve this ad because some things are more important than politics." This is probably the most insulting part of the whole ad. How can Bilbray claim that some things are more important than politics when he is clearly using his daughter's cancer to try and win a political election! Frankly, I find the whole thing rather sordid and disgusting. If Bilbray's daughter is genuinely suffering from terminal cancer (A claim I have no reason to doubt), then perhaps he ought to suspend his political campaign and his congressional aspirations in order to spend more time with his daughter during her final days. To use her in a campaign ad, however, raises serious questions in my mind about the kind of person Bilbray is.
h/t to KPBS