The journalist Jonathan Cohn, an ardent supporter of Obamacare, recently wrote in The New Republic that problems with the rollout of the Affordable Care Act should be “an opportunity to have a serious conversation about the law’s tradeoffs — the one that should have happened a while ago.”

Cohn is right that there was no serious conversation about those tradeoffs back when Congress was considering the law’s passage in 2009 and 2010. But why was that? It was because President Obama and his Democratic allies could not speak seriously — and honestly — about those tradeoffs and still pass their bill.