I'm assuming that they come out in a ring, ordered by the time of their presidency, so Obama and Washington are side by side.
It would begin with a number of grudges being settled. Taft would start lumbering towards Teddy, Carter would attack Reagan like a crazy man, Nixon and Kennedy and LBJ would get into a three-way duel to the death. Clinton would try to opportunistically attack Bush Sr., but W would come to his father's aid. Obama would start running immediately, as John Adams, Thomas Jefferson, James Madison, James Monroe, and John Quincy Adams began running in his direction (in all fairness, it isn't all "kill the black man"; a large part of it is fear of Andrew Jackson).
Andrew Jackson would draw first blood by brutally murdering Martin Van Buren, and then throwing his knife to take out William Henry Harrison as Harrison tried to flee. Jackson would pick up Van Buren's knife and then retrieve his own knife from Harrison's back. John Tyler would be looking agape at Jackson's murderous ways, and would completely miss James K. Polk, Zachary Taylor, Millard Fillmore, Franklin Pierce, James Buchanan, Abraham Lincoln, Andrew Johnson, and Ulysses S. Grant charging towards him. His body would suffer more stab wounds than any other President involved in the competition.
Rutherford B. Hayes, James Garfield, and Chester A. Arthur would form a temporary alliance and encircle and kill Grover Cleveland. William McKinley would be stabbed by Benjamin Harrison as he slowly backed away from Teddy Roosevelt, who had first killed Taft and who was now in the process of gutting the corpse and pulling out the entrails. Woodrow Wilson would be set up by the alliance of Warren G. Harding, Calvin Coolidge and Herbert Hoover; that alliance would be short lived as Coolidge attacked Harding, and then Hoover made an attack of opportunity on Coolidge.
Barrack Obama would run by this scrum, chased by several presidents.
Truman would assure FDR that he had his back, and then stab him as Roosevelt turned to watch his Republican predecessors battle it out. Disgusted by his old boss's actions, Eisenhower would attack Truman, and then perform a mercy kill on JFK (the survivor of the three way battle with Nixon and LBJ).
Having torn out Reagan's throat with his teeth, Carter would be cautiously approached by the duo of Bush Jr. and Sr. Carter would feint towards Bush Sr, and then pivot and stab Bush Jr. in the throat. He wouldn't recover fast enough to prevent Bush Sr. from stabbing his arm, causing him to drop the knife. Bush Sr. would pick up his son's knife and finish off Carter.
As Bush Sr cradled his son's body, ignoring the fray as tears slid down his cheeks, Barrack Obama would run by, chased by several Presidents. As Obama and the chasing Presidents passed the corpse of Taft (lying face down on the floor of the arena) James Monroe would step in a circle of Taft's entrails. The circle would quickly tighten around his ankle, knocking him to the ground, and pulling him screaming towards Taft's corpse.
Ford would walk up behind Bush Sr and put him out of his misery.
Andrew Jackson would jump at the Presidents still stabbing the body of John Tyler, taking out Polk with his right knife and Taylor with his left knife. The other Presidents in that pack would flee, past a sprinting Barrack Obama. Andrew Jackson would casually kill Thomas Jefferson as he passed by, then lick the sweet, sweet blood from the knife blade.
Barrack Obama would sprint past George Washington and Abraham Lincoln, who would be having a polite conversation. As he circled past the corpse of Taft, chased by a pack of Presidents, the pack would shrink by one as John Adams was dragged under Taft's corpse. Distracted by the sound of his father's death, John Quincy Adams would stop and turn, and an expertly thrown dagger would appear in his chest.
Barrack Obama would sprint too close to the pack of Presidents fleeing Jackson, and they'd pick up the chase. Benjamin Harrison would look over the bloodshed in horror, taking small stumbling steps. Sensing weakness, Jackson would kill him. Herbert Hoover would cautiously approach Eisenhower, lowering his knife and offering to make a deal. Having seen what Hoover did to his former allies, Eisenhower would know better than to trust the man at his back. He would take Hoover's hand, and then throw him to the ground and stab him. Ford would then approach Eisenhower, who would sadly agree to an alliance. Together, they killed Rutherford B. Hayes as he ran past chasing after Obama.
Franklin Pierce and Millard Fillmore would be dragged screaming under the mound of corpses growing around Taft's corpse. James Buchanan would be stabbed in the back by Ulysses S. Grant as they chased Obama, as would James A. Garfield. Andrew Jackson would take Andrew Johnson's head off when he fell behind, and then throw Johnson's head at James Madison with enough force to kill him instantly.
At this point, there would be eight Presidents standing on the field. George Washington and Abraham Lincoln would be politely talking next to Washington's entrance. Andrew Jackson, eyes wild, would be searching for his next victim. Ulysses S. Grant and Chester A. Arthur would be chasing Obama. Dwight Eisenhower and Gerald Ford would be considering their options. And Barrack Obama, running for his life.
The Ford and Eisenhower team would decide that Jackson was the largest threat remaining and would go after him. Even working together though, they'd be no match for him. Jackson would cut out Eisenhower's eyes, then hamstring Ford, and then finish them both. Meanwhile, Obama would slip on a patch of blood. As Arthur and Grant closed in, knives would appear in their throats.
Lincoln and Washington would have saved Obama. As Washington recovered his own knife from Arthur's body and Lincoln's knife from Grant's body, Lincoln would help Barrack Obama to his feet. ”I want you to know, son, that I am truly and deeply honored that the country has come to a point where a man such as yourself could become President." Washington would nod as he handed Lincoln back his knife. ”You've been a credit to the office," George Washington would add, shaking Obama's hand.
”Thank you, sirs, I-” Obama would start to say, and then trail off as Lincoln and Washington murdered him.
Cackling mad laughter would ring out across the arena as Jackson approached Lincoln and Washington. The battle would be epic. Legendary. But in the end, Jackson would win. Bleeding from dozens of minor wounds, his rage unabated, he would stand over the corpses of Washington and Lincoln and howl in victory, the last President standing.
Ignoring the jeers and the catcalls from the audience, he would look over the carnage for the corpse of John Quincy Adams so he could piss on it. Seeing it atop the pile of corpses in the center of the arena, he ambled over, flourishing his blades. And as he undid his breaches, THEODORE FUCKING ROOSEVELT burst out from his hunter's blind, duel-wielding battle axes he had fashioned himself from the thigh bones of McKinley and the knives of the other fallen Presidents. Screaming in fury, his fly down, Jackson would attack Roosevelt with his bare hands.
Roosevelt's left axe would be knocked away by Jackson, his right axe would embed itself too deeply in Jackson's leg to be removed. They'd fall to the arena floor, and Jackson would stab Roosevelt in the side. Roosevelt would sneer through the pain, and then close his hands around Jackson's neck. With a twist, he'd snap Old Hickory's neck, and then raise his foe's corpse over his head before smashing it down on his knee to break Jackson's back. Lying bleeding and broken on the ground, Jackson could only glare in hatred as Roosevelt would finish the job.
The victorious President Theodore Roosevelt would raise his hands and shout ”BULLY!"
