Bill Cassidy, R-Cave. Photo: Mark Wilson/Getty Images

The Republican Party’s moderate wing has been in a continuous state of slow-motion collapse for four decades. If there is a single line that encapsulates the process, it is this quote by a senior Republican aide in Congress to Caitlin Owens: “Moderates always cave. I don’t know if conservatives will cave.”

The principle that Republican moderates always cave explains the fate of the health-care bill in the House. When the bill initially failed, it faced opposition from both wings of the party: vulnerable swing-district Republicans who worried that it snatched insurance away from too many of their constituents, and the hard-liners in the House Freedom Caucus who thought it didn’t snatch away enough. Republican leaders solved this seemingly intractable dilemma by moving the bill to the right, bringing the hard-liners onboard, and counting on moderates to cave and support something that was even harsher. It worked.

This also explains the design of the Senate bill. The main barrier to passage in the upper chamber has seemed to be the party’s centrists. Blue- and purple-state Republicans said they wanted to preserve coverage for their citizens who had obtained it through the Medicaid expansion. Bill Cassidy seemed to be leading the moderate wing in a direction that could not be reconciled with the leadership’s agenda. In March, he said, “There’s a widespread recognition that the federal government, Congress, has created the right for every American to have health care.” In May, he attacked the GOP plan for cutting taxes, making drastic coverage reductions inevitable. “I am a critic of the American Health Care Act,” he told the American Hospital Association. “I think it’s to set up tax reform and all the money used for coverage is instead going to be used to pay down the bill for tax reform.”

The Senate bill does not remotely address any of these criticisms. It preserves every cent of the tax cuts in the House bill. It makes health care unaffordable to millions of people with low incomes or expensive medical needs. Astonishingly, it cuts Medicaid more deeply than the House bill. The legislative strategy reflects the assumption that the moderates will cave no matter what.

And so far that strategy appears correct. The only stated opponents all sit on the party’s right wing, setting themselves up to gain leverage to demand pulling the bill even farther right — or, at the very least, prevent it from moving left. How can they possibly pull this off when the bill already sits far to the right of the “moderates” stated parameters? Because the moderates always cave.