(CNN) -- If you watched Barack Obama closely this week you could see where America is heading.
President Obama has said that the United States faces many tough challenges at the moment.
He was outgoing at the parade and parties for his inauguration, greeted well-wishers warmly and danced happily with his wife. But when he took the podium for the first time as the president of the United States, we saw the face of Obama's presidency -- and he wasn't smiling.
Obama has every reason to celebrate. He's now the most powerful man in the world. He has, of course, made history, as the first African-American in the Oval Office.
Our CNN/Opinion Research Poll finds that 84 percent of Americans approve of his performance, which means that even people who voted against him are impressed.
You can feel the excitement worldwide. But at crucial moments in recent months -- accepting the Democratic Party nomination for the presidency in August, declaring victory in the election in November, his inaugural address Tuesday -- Obama seemed like the only one at the party who wasn't enjoying himself. Each time, his speech was surprisingly somber.
This week, he paid very little attention to his remarkable triumph and concentrated on the challenges facing the country. "They are serious and they are many. They will not be met easily or in a short span of time. But know this, America -- they will be met."
One reason Obama didn't seem to have been infected by the euphoria is the imbalance between America's high expectations and its enormous problems.
With the U.S. grinding through two wars and a deepening recession, this is a strange time to celebrate. The party will end quickly. It will be the pain that will last.
So much of the celebration was also, of course, about the color of his skin. Another one of our polls found that 69 percent of black Americans believe that his election marks a culmination of the civil rights movement, realizing the aspirations expressed by Martin Luther King in his famous declaration "I have a dream."
Obama's victory was a landmark, but is his success the signal that centuries of racism in America are over? Once again, expectations may be too high.
Obama's face has a wide, happy and often ironic smile. We've seen that smile this week and we'll see it more.
But right now his presidency has serious work ahead.
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