How should one claim the dividends paid to a broker when short the stock?
It seems to me the right way to do it would be to net the dividend short versus long and report that on 9a of the 1040. The two problems with that are 1) The brokers don't report short dividend payments on their 1099-DIV, so you will trigger disagreements with those documents and 2) It raises the possibility that you would get a negative overall dividend number in line 9a of the 1040, and I'm not sure that is even allowed.
We could report it on Schedule A line 14, as the payment is a percentage of the principal amount of stock shorted, and it is implicitly similar to an interest payment albeit not on a fixed payment schedule.
It could be reported on Schedul A, line 23, but that would have unfair tax consequences and would fundamentally penalize a person for being short a stock.