I would imagine you do so indirectly -- you threaten the income sources (e.g. federal funding to the departments/tax allocation, or killing loopholes), the politics (you publicly advocate for the other guy, or lobby against their prioritized initiatives), or the system itself (advocate for new laws/rulings/governing bodies that would make their lives more painful/goals more difficult to achieve)

It's the presidency -- just playing favorites carries a lot of weight. Or even threatening to cockblock anything they're looking to do for the next 8 years, by swinging party support.