He's agonizing over whether his running would throw the election to Trump. He's agonizing over whether he'd draw enough Trump voters to throw the election to the Progressive-Democrat candidate. He's agonizing over whether that Party candidate would be too Progressive or Socialist. He's agonizing over whether he would have a chance to win.
He's even raising straw men about the fact that he'd be a Jewish candidate.
I am [would be…] running as an American who happens to be Jewish.
At least he's got that much right.
On the other hand, Schultz could quit agonizing and shirt-rending and just run. He could run as a Democrat in the Progressive-Democrat Party and try to draw the Party back toward the center (win or lose, that much would be a valuable service). He could run as an Independent and make his own case for his value as President (did he actually believe in that value).
Sadly, right now—and possibly for the duration—he's just acting like a porch dog, yapping from the safety of his front stoop, without any demonstrated interest in actually joining the fray.