Thousands packed into the cavernous hall at McCormick Place and some have grown weary, even collapsing.
Several seen being carried out of the building in stretchers.
Reports from the arena say those inside are really packed in, making it difficult to even breathe for some. Some of those treated by paramedics appeared to be older in age, reported Chicago Sun-Times reporter Maudlyne Ihejirika.
Supporters grew frustrated at having to remain standing for so long as they awaited Obama amid a sweaty, hot crowd.