Chief Justice Roberts forgot the "faithfully" before the "execute" but put it at the end of the sentence, which made President Obama pause politely to give him a chance to repeat the phrase...which all ended up confusing both of them further as they both started to talk at once. Justice Roberts then added "of America" after "the United States" which President Obama correctly skipped. And - it was freezing cold! Brain freeze, lack of practice, or just way too big a historical moment to think clearly - who knows? At the time it made the President look like he was stumbling, even though it was Chief Justice Roberts who was making all the mistakes. Sadly unfair and a humbling pre-taste of what it means to be President.
Just ask President Bush, who didn't fly airplanes into the World Trade Center, didn't send a Hurricane to the South, and didn't bundle high risk mortgages, but leaves office with very low approval rates due to the way he handled these situations.
Did President Obama handle it well? In hindsight he could have simply repeated what the judge was saying or further down the line of mishaps have said: "No offense judge, but I think we need to do this again" as they apparently might have to - to make sure it is all legal. Or, it was actually handled quite well. I am sure someone is already drafting up new rules for future mishaps - about what a President should say or do if a Chief Judge messes up.
Even the greatest among us remain wonderfully human and prone to making mistakes. It is after all, how we learn and improve things. And, best of all - it keeps us humble.