Former President Barack Obama embedded a hidden message about his Oval Office successor and his political party’s electoral foe in his Democratic National Convention speech Tuesday night, a New York Magazine columnist believes. Behind the funny jabs at former President and Republican nominee Donald Trump, Obama delivered a subtle message about the limitations of rage-fueled rhetoric he urged Vice President Kamala Harris and Gov. Tim Walz (D-MN) to heed, Jonathan Chait argued Wednesday. “Kamala and Tim understand that when everybody gets a fair shot, we are all better off,” Obama told the deleg…