No historical analogy is perfect. But if you want an analogue to the calamitous rollout of healthcare.gov, it’s not the federal response to Hurricane Katrina in 2005. It’s Medicare Part D, the prescription drug program for seniors that the Bush Administration introduced in January 2006.

On Monday, writing in the Washington Post, Ezra Klein reminded everybody of the history: The program’s first few weeks were chaotic, with seniors unable to get their drugs because enrollment into their chosen plans hadn’t worked. Even Republicans called it a disaster. But the Bush Administration fixed the problems and, eventually, it became popular. Today millions of seniors use it to pay for their prescriptions. Nobody talks of modifying the program, let alone repealing it. It’s part of the policy landscape.

Even this analogy, though, has its limits. The most important difference between Medicare Part D and Obamacare has nothing to do with information technology—and everything to do with policy trade-offs. The Bush Administration and its allies weren’t particularly concerned about budget deficits, though they frequently talked about them. And it showed in their drug benefit proposal, which called for spending hundreds of billions dollars in perpetuity—and no new revenues or cuts to offset the new spending. When a government actuary warned that the program would cost even more than the administration projected, the Bush Administration famously tried to squelch the finding. The actuarial projections turned out to be wrong, but the law is still increasing deficits by hundreds of billions of dollars in the next decade alone.

Bruce Bartlett, the former Republican budget official, has the full story at the New York Times Economix blog:

From the beginning, Republicans decided to forgo dedicated financing for Part D. Except for trivial premiums paid by recipients, the entire cost would fall on taxpayers. Moreover, Republicans refused to raise the Medicare tax or cut spending to cover Part D. Hence, the deficit increased by virtually the entire cost of the program. Through 2012, Medicare Part D added $318 billion to the national debt (see “General Revenue” on Page 111 in the 2013 Medicare trustees report). That same report projects that Medicare Part D will add $852 billion to the debt over the next 10 years.

Obama and his allies adopted a very different approach. They made two vows—that health care reform would pay for itself and that, over time, it would actually reduce the deficit. Critics mocked them and, to this day, few people seem to believe them. But the official projections suggest they were good to their word. The Congressional Budget Office has on several occasions estimated the cost of the Affordable Care Act, first upon passage and then following various tweaks to the law. Each time, the conclusion has been the same: A slight reduction in the deficit during the first ten years, with greater reductions after that.