I suspect that many on the left knew at the time Obama was lying about this but kept quiet because they really wanted the law to pass. They won.

[upvoted for giving a crisp recent, and plausible example of people getting away, at least in the short term, with dishonesty. I was a little squeamish about the politicization of the topic but I think it's hard to avoid giving a real political example in a conversation about political dishonesty]

I take the point that there's a complicated collective-action problem here where if enough people repeat something they wish were true, it can become relatively accepted, at least for a while.

The catch is that, as happened here, people often get caught having been dishonest. And we will see how painful the consequences are for those people personally and politically.