Pool reporters traveling with the president said he mouthed what appeared to be some of the words to "The Star-Spangled Banner", but they could not tell exactly what he was saying or singing.
It is also pertinent to mention Trump pushed the national anthem as a partisan issue shortly before the game during a speech to the American Farm Bureau Federation in Tennessee, tweeting, "We want our flag respected - and we want our NATIONAL ANTHEM respected also!" BBC News journalist Anthony Zurcher pointed out on Twitter that it can be hard to hear the anthem on the field, and singing along isn't always easy.
Mr Trump remembered to put his hand over his heart but seemed to forget the lyrics before making a fumbling recovery. Trump struggled to keep up with the rest of the crowd, and critics have charged that the President displayed a lack of knowledge of the anthem's lyrics. But because of Trump's repeated defense of the song and the fact that he likely hears the national anthem more than most Americans, many expect him to know it.
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Trump stayed for half of the game, which he watched from a private box at Alabama's end of the stadium.
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The Flag Code covers aspects of etiquette when the anthem is played in some detail.
He also sang part of the national anthem - starting, then stopping, then starting again - which led some to speculate he didn't know the whole thing.
He said the practice was "ruining the game", and that players who kneel should be immediately fired. "Just show some respect for your country", Don Jr. wrote. He has even changed the banner image on his Twitter account to a photograph of him standing during the anthem before the game.