In that way, the tax debate offers the clearest measure of how powerfully the Republican Party in the Trump era is folding inward. Neither Trump nor GOP congressional leaders are even pretending to represent the entire country—or to consider perspectives beyond those of their core coalition. Instead the party has shown that as long as it can maintain internal unity over its direction, it will ignore objections from virtually any outside source—not just Democrats, but also independent experts, affected interest groups, and traditional allies abroad.

In a best-selling book published during the Reagan years, neoconservative cultural critic Allan Bloom lamented The Closing of the American Mind. The Trump era is crystallizing the closing of the Republican mind.

In several distinct ways, the party is now governing solely of, by, and for Red America. Key among them:

Distorting the legislative process: On the tax and especially the recent health-care bills, the GOP Congress short-circuited the legislative process to minimize public input. Leadership negotiated all the key decisions behind closed doors. That dampened public debate and ultimately forced legislators to vote on massive (and at times handwritten) packages with little time to consider consequences or mobilize opposition. More important, the negotiations took place only among Republicans, denying meaningful input to Democrats or skeptical groups.

Congress has long been growing more partisan, but this still represented a quantum leap in exclusion. Former President Barack Obama made significant changes to his stimulus plan in 2009 to win support from three GOP senators. He also allowed the Senate Finance Committee to delay consideration of the Affordable Care Act for over three months to conduct extended negotiations with Republicans. (No Republicans ultimately backed the ACA on the floor, but that didn’t erase the effort.)

Punishing Democratic strongholds: The tax bills, as I’ve noted before, are not unusual in benefitting GOP constituencies. But they are unusual in consciously punishing so many Democratic-leaning groups, especially in the House bill. Among others, these groups include families in blue, high-tax states, who’d be hurt by restrictions on state- and local-tax deductibility; homeowners in large, mostly Democratic metro areas, who’d face limits on mortgage deductions; and students, who’d face higher taxes on college debt or graduate tuition waivers.

This confrontational instinct extends beyond taxes. Violating conservatives’ usual fondness for federalism, the House passed legislation Wednesday that would force every state to recognize a concealed-weapon permit granted in any state. The administration is seeking to withhold federal grants to pressure so-called “sanctuary cities” that limit local cooperation with federal immigration authorities. And Trump is trying to undermine blue-state regulatory standards by allowing the interstate sale of health insurance.