President Obama highlights success stories of the Affordable Care Act. Truth Teller is an app that uses automatic speech-to-text technology to transcribe political speeches, then searches that transcript for matches in our fact-check database. (The Washington Post)

In his State of the Union Address on Tuesday night, President Obama offered a robust defense of the Affordable Care Act (ACA) — he just left out the one thing everyone’s been talking about for months: The incompetent rollout for which he is ultimately responsible.

“If you have specific plans to cut costs, cover more people and increase choice,” he said to the Republicans assembled in the chamber, “tell America what you’d do differently. Let’s see if the numbers add up.”

Obama’s health-care reform can significantly expand access to decent health-care coverage without blowing up the health-care system to which most Americans are accustomed. It sets out to accomplish an important social goal in a way that majorities in Congress could accept — though just barely. Republicans profess to favor many of the ACA’s outcomes. “No, we shouldn’t go back to the way things were,” Rep. Cathy McMorris Rodgers (R-Wash.) said in Tuesday night’s GOP response. But despite the usually small-bore GOP proposal here and there, the party still has not coalesced behind an approach that has the potential to extend good coverage to as many people and pass Congress.

The president was right to take credit for threading a pretty tight needle, and he was right to stick up for a policy that could still do a lot of good in the coming years, particularly for the uninsured.

But he needed to discuss one of the greatest failures of his presidency — the poor rollout of the ACA. That’s not just because it would have been the honest thing to do, or only because the rollout has defined the year since his last State of the Union address more than almost any other issue, or merely because leaving it out made the section seem bafflingly incomplete to anyone who would tune in to watch the whole speech. It’s also because he needed to draw a clear distinction between the foibles that have threatened the phase in of reform and the reform’s fundamental design — which the early mistakes haven’t proven unworkable. He can’t strike that contrast, making the best case for following through, without talking about how and why he and his administration messed up.

UPDATE, 10:40 a.m.: Minor edits made above for typos and clarity.

Stephen Stromberg is a Post editorial writer. He specializes in domestic policy, including energy, the environment, legal affairs and public health.