When Obama entered the White House, the economy was in a freefall, the auto industry was collapsing and more than 4 million Americans had lost their jobs, said Emanuel, now Chicago's mayor.
When asked which crisis he wanted to tackle first, Emanuel said Obama told him, "We were sent here to tackle all of them."
"We faced a once-in-a-generation moment in American history and fortunately we had a once-in-a-generation president," said Emanuel, Obama's chief of staff from 2009 to 2010, when he resigned to make his mayoral run.
Emanuel spoke of reforms to healthcare, Wall Street and education, saying after each: "That was a change we believe in. That was a change we fought for. That was a change President Obama delivered."
Concerning the auto bailout, Emanuel said, "Where [Republican presidential nominee] Mitt Romney was willing to turn his back ... President Obama said, 'I got your back.'"
Emanuel said sometime during the next four years "an unforeseen crisis will show up ... and seize our country," then asked who the crowd wanted in the White House.
Would they want the man who said, "Let Detroit go bankrupt?" Emanuel asked, or "a president who had another four words, 'Not on my watch.'"
Whoever occupies the White House after the November election "will shape not just the next four years," Emanuel said, adding America needs "proven leadership, proven judgment and proven values."
"America needs four more years of Barack Obama," he said.