"Preemption has gained a new valence during this time of heightened political polarization. Tensions between governors and mayors have escalated in past few years with the tendency of republican-leaning state legislatures to preempt and even punish democratic-leaning local governments for enacting policies such as designating themselves as a “sanctuary city” to shield their undocumented immigrant population from the harsh deportation practices of the federal government. Mayors pushing progressive agendas are increasingly running into a wall of conservative state resistance through what some view as aggressive, and even “nuclear”, state preemption. There are hints of resistance that runs the other way as well, with more conservative cities and counties enacting “second amendment sanctuary” resolutions in response to the adoption of stricter gun controls by more progressive state legislatures." How does partisanship, or party politics, cause tension in a federalist government system?