Bart does actually understand the United States Constitution, as evidenced by a number of quotes associated to him. "Spitballs are not free speech" "The first amendment does not cover burping".
Remember, Bart isn't 10 years old as depicted in his television program. He's been 10 for 12-13 years, thus he's in his early 20's.
He knows quite a bit about Springfield, and all the mischief which centers around this city in Illinois, since he attends Springfield Elementary. After all, mischief is part of his natural character, thus positions him perfectly in grasping the ability to participate in all the scams perpetrated on the American public. (no on the job training involved here)
Bart has his own credit card 4123 0412 3456 7890. (No need for a taxpayer card).
One of Bart's pets is an elephant, named Stumpy. (This may make him a Republican in disguise)
He understands the need for planning and implementing, as evidenced by several quotes from the past. "Relax Lis, Dad and I always have plan B" "You probably should have researched this, Eh Dad". (With Bart, comes Homer Simpson, for FREE)
AND LASTLY, ACCORDING TO BART.. I didn't do it, No one saw me do it, No one can prove anything. (what a possible candidate)