President Obama messed up the oath of office on his inauguration day not once -- but twice

If Donald Trump's presidential oath of office goes smoothly on Friday, he will be the first person to be sworn into office without making a mistake in 12 years.

While Barack Obama may have been known as the better wordsmith and orator than George W. Bush, Bush was actually the last president to take the oath of office smoothly -- because Obama flubbed it not once, but twice.

The first time wasn't his fault. Supreme Court Justice John Roberts accidentally reworded the oath ever so slightly, saying "execute the Office of President to the United States faithfully" instead of "faithfully execute the Office of President of the United States."

Obama paused and smiled, seemingly aware of the mistake. He then retook the oath the following day out of an "abundance of caution" -- inviting Roberts to the White House the next day. Obama admitted he did not swear on a bible for this second administration of the oath, but insisted in was binding anyway.

But the blame for the flubbed oath fell on Obama's shoulders four years later, when in 2013 he failed to fully enunciate the word states as he said "Office of President of the United States."

But in that case the president did not have to retake the oath again. He had already given it the day prior at noon. January 20 fell on a Sunday in 2013, forcing inauguration festivities to be scheduled for the following day, but the Constitution required the president to take the oath at noon on January 20.

That is the only oath he ever took that went off without a hitch, earning him a "good job" comment from daughter Sasha Obama afterwards.

Watch Obama's 2013 oath of office:

Anyone looking to keep track of whether or not Roberts and Trump pull off a perfect oath, here's the exact language they'll both be saying come Friday.

"I, Donald John Trump, do solemnly swear 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."