Donald Trump's swearing-in went perfectly - things didn't go so well for Obama in 2009

For Supreme Court Chief Justice John Roberts, Friday's inauguration of President Donald Trump couldn't have gone any better.

It has nothing to do with politics - and everything to do with the judge's flawless recitation of the oath of office as Trump was getting sworn in.

Roberts wasn't so fortunate eight years ago in 2009, during Barack Obama's first inauguration. In that ceremony, as Roberts led Obama in the 35-word oath, he memorably recited one of the words out of order, causing Obama to hesitate in a brief moment of awkwardness.

Article II of the Constitution required Obama to say he "will faithfully execute the Office of the President of the United States." But Roberts, reciting the passage from memory, placed the word "faithfully" at the end of the clause - "I will execute the Office of President to the United States faithfully," he said.

The deviation from the original text tripped Obama up, and he momentarily paused after the word "execute." Realizing his mistake, Roberts repeated the clause, starting with the word "faithfully" - resulting in "execute faithfully," which is still incorrect. Obama answered back with Roberts' original incorrect recitation of the oath, and broke out into a smile over the confusion. (No one seemed to notice that Roberts originally said "President to the United States" instead of "of the United States.")

The incident may have arisen from Roberts' adherence to a dubious rule of grammar that says a two-part verb, such as "will execute," cannot be split up by an adverb, such as "faithfully." Roberts has a history of grammatical pedantry, linguist Steven Pinker noted the day after Obama's inauguration, and as Roberts recited the oath, his persnickety instincts may have caused him to inadvertently transpose the words.

Conservative pundits immediately pounced on the blunder. Fox News anchor Chris Wallace even openly wondered whether Obama was actually president.

"I have to say, I'm not sure that Barack Obama really is the president of the United States, because the oath of office is set in the Constitution," Wallace said during Fox News's coverage of the inauguration.

He was - Obama officially became president five minutes earlier when the clock struck noon. Constitutional experts also chimed in, saying the flub didn't affect Obama's status as president.

But to quell the rumors, Obama and Roberts took part in another swearing-in ceremony the following day, and it went off without a hitch.

Four years later, for Obama's second inauguration, Roberts read the oath from a notecard. This time, it was Obama who messed up, hesitating on the word "states" in "United States," and never fully enunciating it.

That misstep got much less attention than the one in 2009. But the point was moot - Inauguration Day fell on a Sunday that year, so the public ceremony Americans viewed on Monday was just for show. Obama had already taken the oath of office in private the day before.

Here's the full text of the oath of office:

"I do solemnly swear (or affirm) that I will faithfully execute the office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States."