People keep telling me it’s madness, this Republican effort to replace Obamacare with a toxic policy they know will cause human and political carnage. Why would a party want to pass legislation that promises to cost millions of people their health insurance while raising rates and denying benefits to tens of millions more? The answer lies in the structure of public opinion, something I discussed at some length last year as a reason for the rise of Donald Trump. It hasn’t changed appreciably since then, and it’s worth revisiting as a way of making sense of our seemingly inexplicable politics.

A key reason why the United States is historically so moderate is because public opinion is generally centrist. There have always been meaningful differences between liberals and conservatives and through the years the center of gravity has fluctuated between left and right, but our differences have traditionally covered a narrow and continuous slice of the ideological spectrum. This gave the parties incentive to go fishing in the middle of the pond where the voters were.

For many years, the center leaned toward the right side of this narrow band, but that began to change when the coalition of young, coastal and multicultural voters that elected Barack Obama in 2008 brought to fruition a trend that had been building for years, posing an existential threat to the Republican Party as constituted if this coalition were allowed to grow large enough. Rather than chase Obama voters with conservative alternatives that would likely make them an opposition party in a new political alignment, Republican leaders responded by delegitimizing Obama and his supporters in a ploy to maintain the status quo political alignment where they were dominant. Over time, this had the effect of radicalizing the Republican base and uniting it in tribal opposition to the left, creating a distinct and disconnected second mode of public opinion. Aggrieved and alienated, these voters were primed to respond to Donald Trump’s reactionary populism after years of feasting on the conservative media’s portrayal of Obama as an alien other who was the sworn enemy of America as they imagined it. Their view of the country began to deviate sharply from the larger pool of public opinion where Democrats and independents lived. They were residing on Republican Island.

Obamacare became symbolic of this divide, and when Congressional Republicans voted over and over to repeal it they were telegraphing to their voters on Republican Island that they would stop at nothing to defend the nation from alien forces. To everyone else, Obamacare was just a healthcare plan that was and is regarded with the normal array of support and disapproval. Not so on the Island. And if Republicans couldn’t make good on their promise to defend the Island now that they control congress and the White House—well, why should their voters continue to let them control congress and the White House?

And when will another chance like this come along? Republican leaders see the anger on the mainland and know that continued control of the House isn’t guaranteed after next year. But right now they do run everything. If they are willing to ignore popular opinion and deal with the fallout after the fact, they are uniquely positioned to bring about a massive upward transfer of wealth by taking an axe to social welfare spending—the one constant in their agenda that unites party elites and serves the interests of those who pay the bills to maintain the Island. It meant writing the legislation in the dark without debate and springing it on the public, but there were no better options in a system designed to make it difficult to govern against the will of the majority. It’s impossible to imagine something like this happening if public opinion looked like it traditionally has.

Mitch McConnell is fully aware of the damage his Senate bill will do to many of his own constituents and he certainly understands the long term risks of owning a health care law that people will hate. But he is motivated by power and survival, and he recognizes that not delivering on repeal is the most immediate threat to both. Like Trump, he is governing for public opinion on the Island and the wealthy interests that own the land. That’s how we ended up where we are.