“There is a strong and aggressive focus [in the Trump White House] on using these strategies to go after states that are not in the president’s corner in ways that have an enormous amount of technical sophistication to them,” says Don Kettl, a professor at the University of Texas at Austin who studies state-federal relations. “They are doing it in ways that previous administrations haven’t tried. So this is a very big thing. It has the possibility of casting a very long shadow over not only the next few months, but also the possibility of a second term.”

While Democrats and Republicans both claim to revere the principle of states’ rights, each side, while occupying the White House, has at times leveraged federal authority to override state decisions. The general trajectory over the past quarter century has been toward steadily rising conflict between presidents of one party and states controlled by the opposing party.

Read: Federalism is dead, long live federalism

During the relatively less polarized 1990s, former President Bill Clinton managed to build alliances with Republican governors, such as John Engler of Michigan and Tommy Thompson of Wisconsin, on issues such as welfare reform. But by the time Obama took office in 2009, coalitions of attorneys general from Republican states were routinely filing federal lawsuits challenging his policies. Those Republican lawsuits blocked several Obama initiatives, including his efforts to limit carbon emissions from electricity generation and to provide legal status to about 4 million undocumented immigrants. The Obama administration, in turn, launched lawsuits against some Republican states seeking to limit access to voting; Obama’s Justice Department also sued to block Arizona’s “Show your papers” law targeting undocumented immigrants.

Still, Trump and Republicans in Congress have escalated these skirmishes to a new level. “I can’t really recall a federal administration that has so aggressively and on so many fronts claimed federal powers to supersede state authority,” says Richard Frank, who studies environmental law at the University of California at Davis.

Through both legislation and executive action, Trump and congressional Republicans have pushed a series of policies that target blue states, starting with the tax bill passed in late 2017. That law sought to pressure blue states to cut their own taxes by capping what taxpayers could deduct in state and local taxes from their federal tax returns. (Almost all of the states in which the largest share of taxpayers claimed these deductions in 2016 voted for Hillary Clinton that year.)

Trump has also tried to pressure so-called sanctuary cities that don’t fully cooperate with federal immigration enforcement by withholding law-enforcement funds from them. And his Justice Department has sued California over its “sanctuary state” law.