I guess we can't be sure about all of the previous Presidents. Many of their youthful indiscretions were not recorded for posterity.
I'm thinking Sam Houston might have eaten dog while he was living with the Indians, but I guess when "the republic" is used without further specification it means "the United States," not the Republic of Texas.
Will the young Barack Obama who ate dog go down in the annals of legend like the young George Washington who cut down the cherry tree but then confessed it out of conscience? (This sounds possibly in character for Washington, who actually struggled to keep his own bad temper under control. He might have caught his head on it while horse riding, and in a fit of pique cut the whole blankety-blank tree down, no matter how valuable it was.)